The most important Web.config value for the Atalasoft cache is:

<add key="AtalasoftWebControls_CacheLifeTime" value="60"/>

What is yours set to?

In general, it is best to set this value to same length of time your "Session timeout" is set to.  You can find this value by following these steps:

1. Load up the IIS control panel
2. Right click on the web application in question, and select "Properties"
3. On the "Virtual Directory" tab, click the "Configuration" button
4. On the "Application Configuration" dialog, select the "Options" tab, under "Enable session state" there should be a value marke "Session timeout"