right click and opening files is really slow!

I can explore my folders and right click without problems but it takes a long time 1 minute or more to open files or to even to get right click menu. The problem goes away when I disable the network connection. I'm on a university Novell LAN so I'm wondering if that is the problem. It started today without any reason. Can any one help me?

Windows XP Pro with lots of memory and a good processor.