Vista - Can't Access Network Computers Suddenly

I am having trouble seeing other computers on our network all of a sudden. I am on an Acer Aspire 5920 running Windows Vista Home Premium and the other computers are running Windows XP. I've had my computer for almost 1 year without having this problem, but all of a sudden I can't see the other computers in the network. The other computers are able to access my shared files. The really strange thing is if I go into any programs that have a network file as a recently opened file (under the File menu some programs store the latest few files you accessed) I can open, modify, and save it, but I still can't see the computer in the network locations. I also noticed in Wordpad that by default it opens to a network computer when I hit file->open and I can open files on that computer, but that same computer still doesn't show up if I browse to the Network folder. Any ideas on this?

We were able to fix this by unplugging the router and shutting down all the computers.