I wonder if anyone can help?

I've got a set of HP4525s laptops that I'm trying to connect wirelessly to our Novell servers, but I'm getting a lot of "Tree or Server Cannot Be Found" errors. It doesn't happen all the time, but it is very regular.

The laptops all have Windows XP sp3 and Novell Client 4.91sp5 and a BroadCom 4313 built-in wireless card, and are connecting to a Cisco 4402 wireless controller running AirLap 1131 APs. The servers are NetWare 6.5. I've looked at the various posts that have already been made here but nothing seems to work.

I'd be very grateful for any pointers!

Many thanks,