Java GUI very slow on 7.5.0.6 server

I administer a few Master Servers, and for one of them, ever since we upgraded it from 7.1.0.4 to 7.5.0.6, signing in and generally working using the Java GUI is very slow. I don't have the same problems with the other servers (same OS, same NBU version, etc.).

It is a Master/Media server running SLES 10 sp3 and NBU 7.5.0.6

I am loggin in from a Windows XP SP3 32bit and from a Windows 7 SP1 64bit.

Any ideas what can I check?