we have the following problem:

WindowsXP SP2
Netware Client 4.91 + SP1
Netware 6.5 SP4a

When users are already logged in (ws only or not does not matter) they
are not able to browse for Netware trees from within the Netware client
anymore. However if you manually enter the name of the tree you can
browse the ds structure and are also able to login without any problems.
This problem disappears as soon as the user belongs to the local admin
group. If the user is a normal user the problem reapperas. The problem
also not exists if the user is not logged in at all.

Any ideas hiw to fix that behavour?
Thank's for your help.