Question : 2003 Terminal Server logon issues, Stale sessions?

Recently I deployed a Windows 2003 terminal server environment for roughly 26 - 30 users. It is running perfectly well except for an intermittent an rather puzzling problem.

Occasionally when a user logs on they are prompted for their logon credentials which are entered correctly and the session appears to hang. The user is shown the grey background colour on their desktop but no start menu or desktop icons. The only way we can free the logon for the user is by resetting the session via terminal services manger. If the user disconnects from their stale session and reconnects they still have the same problem.

There is nothing in the event viewer regarding this problem on either the server or the clients. In the office we are using HP thin clients with XP embeded and RDP 6.1 externally the users have their own laptops running XP pro. However I have suggested it may be the laptops client software causing the problem but it happens to office based users who don't use a laptop externally also. There seems to be no time correlation nor does it make a difference if the user logs off their session or simply disconnects the problem will happen intermittently to different users, different pcs and following different logon practices. Im not sure what to check first.

Any help would be apprectiated.

Answer : 2003 Terminal Server logon issues, Stale sessions?

I tried all of the above mentioned tweeks to no avail. I eventually phoned Microsoft and although I had seen this KB article, because I was unable to complete step 1 I did not proceed to step 2 which is a list of registry changes.  
Here is the article: http://support.microsoft.com/kb/324446

It basically has you set maximum and minimum workload thresholds on the terminal server and add a key which refreshes a sessions registry file frequently.

I could not do step 1 of the article because of the raid array the drives are running on but the chap from microsoft said they consider it good practice to make the changes mentioned in step 2 if you encounter problems on terminal server.

So thanks for all your suggestions anyway but this aKB article fixed it.