On one strange occasion, with proper permissions and firewall settings set, my notebook running Windows 7 (Computer A) cannot display ANY computers on the network except for itself.
The Windows XP machine (Computer B) was correctly displaying the other computers in the network correctly. The other Windows XP machine (Computer C) was also listing everything correctly.
All the computers could ping each other correctly, except Windows Explorer got confused when trying to find them. Typing in the path manually didn't work either.
When trying to access Computer A from Computer B, I was prompted with a password dialog. Strangely enough, even though I typed the correct information it wouldn't let me connect.
So what was wrong with Computer A running Windows 7? For some reason, it was connected to both my wireless network and VMWare virtual network.
After doing a little snooping, I discovered that it was the "VMWare DHCP Service" and "VMWare NAT Service" services which were messing with my wireless network settings.
Go into the "Services Manager" (by running "services.msc") and stop the services mentioned above. Don't disable them, only stop.
Refresh the network browser and the other computers should display properly.