Network resources not accessible to Users

We have a LAN with two servers running Windows 2003 server. One is the network server the other the mail server. All other computers are running Windows XP SP2.

Sometimes users can’t access the network resources when they log in as them; so i log off and log in as the administrator it works, log off and log in again as a user, VOILA! Everything is back to normal. This has happened several times and that is the solution i have been offering.

Is there a permanent solution for this?

Dan