Dug this up for you.

It's definitely the Netware client doing this, at least for me.

What happens: right-click over a quick-launch toolbar icon, or over a desktop shortcut. It takes about 10-25 seconds before the menu pops up. Try again, any icon, and it's fast. Wait about 5 minutes, and it is slow again.
Does not affect My Computer, My Net, Recycle, or system tray icons.
It happens on Windows 2000 SP4, but not on Windows 2000 SP3.

During the delay, Task Manager shows nothing going on. But Ethereal (a network tracer) shows that the Netware client is the culprit. It looks to me like the PC is using the Netware client to try to resolve a name using IPX SAP, SLP, and Bindery scan.
There are multiple requests using each protocol with 1-4 seconds delay between them, acounting for 12 seconds from
the time I clicked till it finally gives up and then I see the menu.
I hestitate to say it is trying to resolve the name "C" using the network, but that's what it kind of looks like to me. Amazing if true.

I have Novell Netware Client 4.83, with some patches. If I uninstall the client, the problem goes away. I've tried 4.83 service pack 2, and 4.83 service pack 2 plus update "e". No difference - still slow. Reports elsewhere say that client 4.90 does not fix it either.

If you're having the same problems and using the Novell client, then the best place to follow up is probably on Novell's newsgroup:
novell.support.os.client.winnt-2k-xp

Hope this helps