Profile Corruption

I have gone through all of the current XP questions and have sort of got an idea of the slow done that my clients get.

THe other issue I am getting is the profiles on occasions will get corrupted in a manner to which I have to reset their profiles on the Win2k AS.

When Logging in the profile will see the blue background of the desktop, then after about 30 seconds it will offer an invalid user denial or invalid DNS server. After this the profile is unusable.

I have set my DNS server under the TCP/IP properties but havent got any LM host file in any. Is that related. I also initially thought my network at the Physical layer is has too much traffic but it is fully switched.

Can anyone recommend a good network monitoring program to monitor across a switched network?

Regards,

Andre