Drive mappings disconnect and connect all the time after PDC probl

Hi,

We have an odd situation going on here; a few days ago after installing SP1
of win2003; our pdc became very slow and this resulted in huge problems on
our network. We promoted our backup DC tot PDC and disabled the DHCP and DNS
services on our former PDC, that resolved the issue of DHCP and DNS problems.
All the clients have a logonscript that connects shared folders on the
fileserver to some drive maps.

When they login, the drive maps are being created, but after a certain
amount of time, the drive maps disappear; they become unavailable. Some
minutes later, they re-appear again and we can connect to them.

Does anyone have a hint (or the solution :-)) where we can look for this
problem?
Thanks !