Process dxalw32.exe starts but no GUI

Our setup is XAL v3.5.x on Windows Server 2003 Terminal Server with MS SQL Server on seperate server.

Every now and then a user looses connection to the XAL program during say processing an invoice. The User then has to close XAL by force ending the process in Task Manager.

After that XAL will not start the graphical part. The process starts fine (can be seen in Task Manager) but no window is presented, no error is shown and hence the user can no longer use XAL.

Last time this happend a new profile on the terminal server had to be created for the affected user.
Can anyone tell me where in a user's profile XAL stores temporary files and (maybe) locks that if not properly closed can cause this situation?

A user logout/login does not solve the situation.
If I login to XAL with the affected user's credentials all is well.

Any help will be greatly appreciated.