No programm access from start.

Hello all,
We have about 300 XP machines running on an NT4.0 network. On several of them, when you go to, “start button >all programs” nothing shows up; it does nothing. Some of them, going into “my computer” it stops reponding and I have to close it through the Windows Security window (Ctrl+Alt+Delete). I have run: a couple Adware utilities, a virus scan (updated) and cleared all the restrictions, in the policies running from the NT machine. On one machine, I made the user an administrator of that machine.
Any ideas? Something simple I am missing?

GP