Can't Access Shared Files After AVG Install

We have four computers on the home network running various OSs - win98, win2000, xp (don't think I need to post all specs of each system for this.) I recently dumped Norton AV and installed AVG Free on all computers. Prior to this install, all files/folders that were shared on the network were accessible from all computers. Since the AVG install, no access to them anymore.

I should also mention that the only firewall on the network is the router's firewall (netgear). (And I don't believe AVG Free has an integrated firewall - is that right?)

I can still see the whole network in My Network Places but I get a "path is not valid" error message when I try to access the shared files (from any computer). When I turn off AVG, access to the shared folders resumes. So it has to have something to do with AVG that's causing this.

I have searched and searched for an answer or workaround to this (here, AVG forum, googled it, etc) but can't find one. The closest thing I have found is this:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;177078
however I am not getting those same error messages so I don't want to mess around with the registry if that's not the problem.

Any ideas?

Thanks --
thealu