Can't access WORKGROUP PC's on network? Locks up.

My computer all of a sudden can no longer find any other workstations in the
WORKGROUP network. The network card drivers seem to be ok and I still have
Internet access. When I click on the Network it takes a while for the
WORKGROUP icon to come up (20 seconds), and when I click on that I get
nothing. What are the steps to fix this?

Not sure what caused the problem but I recently installed anti-virus
software so I have now uninstalled Windows One Care. Also did try Norton
AntiVirus recently and have that uninstalled.

Using the latest version of WinXP.