GroupWise WebAccess was installed on Windows 2003 Server in a DMZ. After 20 minutes, the user would timeout and couldn't reauthenticate using her GroupWise username and password. The only way to reconnect was to use a local username/password on the Windows system.
The IIS service account didn't have permissions to access the directory where the webaccess agent wrote temporary files. To fix this, we granted write/modify/execute permissions to c:\novell\webaccess\users directory to the iwm_machinename user, and now it works fine.