Occasional internet connection problem!

I just want to gather some suggestions on the causes of the following web access problem:

I use win2000pro and IE5 to access internet quite well. Recently, after I visited few sites e.g. hotmail/yahoo, IE works at the very beginning but fails to display other sites very soon (Note: it claimed that website found in the status bar) The logo turning round and round. And a long time later, the fail page occurs. I tried to update to IE6, or use Netscape, still have this problem. I have to restartor re-login the computer.

What I have done recently is to install the NetBEUI protocol to allow communication between systems of the same workgroup.