Strange behavior in Network Browsing Applications

"From the sounds of it you may have set each pc to do it's own dns lookup on opendns through their individual network configuration screens. Probably a better way to do it would be to set the DNS settings on your router to be the opendns servers then configure the clients to use the router as the dns server. This would allow the router to name resolution for the local network while still using opendns for remote connections.

As far as the issues with the workgroup goes I think that is down to one PC declaring itself the master browser in the network and storing the different computers connections see this article http://en.wikipediadotorg/wiki/My_Network_Places

If you have one PC which is on all the time turn off the computer browser service on all the others to force that one to be the master browser."