Hello,

Our scanning application (using DotTwain 8.0) works fine on most of our workstations running XP Pro.
However on some workstations the app freezes after the Acquire() method.
The CPU utilization goes up to 50% (on a dual core CPU) and does not respond anymore.
This problem arises with some of our Fujitsu fi-5120C scanners, but not on all of them.
We have the latest Twain drivers installed (9.21.720.0).
The workstations where the problems occur, work fine using the WIA interface.
The last part of the tracelog shows this:

Atalasoft.Twain: 10:16:39:89 - TwainController: SetCapabilityValue(CAP_FEEDERENABLED), State = SourceOpen
Atalasoft.Twain: 10:16:39:89 - TwainController: AOV, capability = CAP_FEEDERENABLED
Atalasoft.Twain: 10:16:39:89 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:89 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:89 - TwainController: AOV, item type = TWTY_BOOL
Atalasoft.Twain: 10:16:39:89 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue(CAP_DUPLEXENABLED), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: AOV, capability = CAP_DUPLEXENABLED
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: AOV, item type = TWTY_BOOL
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue(ICAP_SUPPORTEDSIZES), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: AOV, capability = ICAP_SUPPORTEDSIZES
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: AOV, item type = TWTY_UINT16
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:90 - TwainController: SetCapabilityValue(ICAP_UNITS), State = SourceOpen
Atalasoft.Twain: 10:16:39:90 - TwainController: AOV, capability = ICAP_UNITS
Atalasoft.Twain: 10:16:39:90 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: AOV, item type = TWTY_UINT16
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: SetCapabilityValue(ICAP_XRESOLUTION), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: AOV, capability = ICAP_XRESOLUTION
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: AOV, item type = TWTY_FIX32
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:92 - TwainController: SetCapabilityValue(ICAP_YRESOLUTION), State = SourceOpen
Atalasoft.Twain: 10:16:39:92 - TwainController: AOV, capability = ICAP_YRESOLUTION
Atalasoft.Twain: 10:16:39:92 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:93 - TwainController: AOV, item type = TWTY_FIX32
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:93 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:93 - TwainController: SetCapabilityValue(ICAP_PIXELTYPE), State = SourceOpen
Atalasoft.Twain: 10:16:39:93 - TwainController: AOV, capability = ICAP_PIXELTYPE
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:93 - TwainController: AOV, item type = TWTY_UINT16
Atalasoft.Twain: 10:16:39:93 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:95 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:95 - TwainController: SetCapabilityValue(CAP_INDICATORS), State = SourceOpen
Atalasoft.Twain: 10:16:39:95 - TwainController: AOV, capability = CAP_INDICATORS
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:95 - TwainController: AOV, item type = TWTY_BOOL
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand(CapabilitySet), State = SourceOpen
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:95 - TwainController: SetCapabilityValue, CapabilitySet = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:95 - TwainController: GetCapabilityValue(CAP_FEEDERLOADED), State = SourceOpen
Atalasoft.Twain: 10:16:39:95 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceOpen
Atalasoft.Twain: 10:16:39:97 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:97 - TwainController: GetCapabilityValue, CapabilityGetCurrent = TWRC_SUCCESS
Atalasoft.Twain: 10:16:39:97 - TwainController: RC, capability = CAP_FEEDERLOADED, container = TWON_ONEVALUE
Atalasoft.Twain: 10:16:39:97 - Getting ONEVALUE data
Atalasoft.Twain: 10:16:39:97 - TwainController: GetTwainObject, 2142194, TWTY_BOOL
Atalasoft.Twain: 10:16:39:97 - TwainController: ConvertObjectType, True to System.Boolean
Atalasoft.Twain: 10:16:39:97 - Types: System.Boolean, System.Boolean
Atalasoft.Twain: 10:16:39:97 - TwainController: SendCommand(UserInterfaceEnableDS), State = SourceOpen
-- FREEZE... --

A log from a succesfull scan on another workstation looks exactly the same, but continues after the SendCommand(UserInterfaceEnableDS) line with the following lines:

Atalasoft.Twain: 11:47:59:34 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 11:47:59:34 - TwainController: ProcessEvent = TWRC_DSEVENT
Atalasoft.Twain: 11:47:59:34 - TwainController: InitiateDataTransfer
Atalasoft.Twain: 11:47:59:34 - TwainController: GetCapabilityValue(ICAP_XFERMECH), State = SourceEnabled
Atalasoft.Twain: 11:47:59:34 - TwainController: SendCommand(CapabilityGetCurrent), State = SourceEnabled
Atalasoft.Twain: 11:47:59:34 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 11:47:59:34 - TwainController: GetCapabilityValue, CapabilityGetCurrent = TWRC_SUCCESS
Atalasoft.Twain: 11:47:59:34 - TwainController: RC, capability = ICAP_XFERMECH, container = TWON_ONEVALUE
Atalasoft.Twain: 11:47:59:34 - Getting ONEVALUE data
Atalasoft.Twain: 11:47:59:34 - TwainController: GetTwainObject, 1989898, TWTY_UINT16
Atalasoft.Twain: 11:47:59:34 - TwainController: ConvertObjectType, 0 to System.Int32
Atalasoft.Twain: 11:47:59:34 - Types: System.UInt16, System.Int32
Atalasoft.Twain: 11:47:59:34 - Converting UInt16...
Atalasoft.Twain: 11:47:59:34 - TwainController: InitiateDataTransfer, ICAP_XFERMECH = 0
Atalasoft.Twain: 11:47:59:34 - TwainController: InitiateDataTransfer, Starting Acquire Loop
Atalasoft.Twain: 11:47:59:34 - TwainController: SendCommand(ImageInfoGet), State = ReadyToTransfer
Atalasoft.Twain: 11:47:59:35 - TwainController: SendCommand = TWRC_SUCCESS
Atalasoft.Twain: 11:47:59:35 - TwainController: ProcessNativeTransfer, Starting transfer...
Atalasoft.Twain: 11:48:02:42 - TwainController: ProcessNativeTransfer, Native transfer result = TWRC_XFERDONE
Atalasoft.Twain: 11:48:02:42 - TwainController: ProcessNativeTransfer, TwainDataTransfer = False
Atalasoft.Twain: 11:48:02:42 - DibToBitmap: hMem = 57213220
-- ETC ---

In what direction should I look for further investigation?

TIA.

Based on the log it looks like we are making a call into the driver and the driver never responds.  There isn't much that can be done about that, but here are a couple things to try:

1. Change the value of Device.ModalAcquire.  Sometimes having ModalAcquire set to true will help, but if the same driver works on other systems it probably doesn't matter.
   
   
2. Check if TWAIN 2.0 is installed on the system.  I have a Fujitsu and some early versions of TWAIN 2.0 would cause crashing and lockups.  Look for "Windows\System32\twaindsm.dll" on the system that does not work.  If it's there, either rename it and see if that solves the problem or install the latest version of TWAIN 2.0 from here.