Hmm - what's wrong with "NT4"?
I worked with a client a while back who was having strange and intermittent issues related to authentication and connecting to the domain during the login process (represented as authorized drive mapping failures). I modified the login script to do a full environment dump when we could not reproduce their issue/symptoms. What we found was that when the domain connection failed, the corresponding environment values were undefined. In some cases the entire environment was blank! (yeah - open a command prompt, type SET, get no output - if you could do that during logon). The thing that made this tough to troubleshoot is that if you dumped the environment after the login process completed, it was fine - it was just incompletely defined during the initial login process.
I can't provide any actual resolution because only 4 his 150+ systems experienced this, and after he re-loaded one and the problem went away, he simply re-imaged the other 3. The key was seeing that the environment was messed up during the logon process, but not after.
We actually moved away from InGroup for group authorization in our login script because of timing and performance issues in large (15-20K+ users) organizations and/or those with lots of security groups. Our script caches the list of groups the user is a member of when the script starts, eliminating lots of InGroup lookups.
You can find more about our Universal Login Script from the User Guide or the product page.
a Rocket Scientist!