Neibourhood can't see others

I have a peer network with 9 machines that has been set up for 7 years. All
of a sudden Network neibourhood can't find any of the serving computers, 1
print server and one file sharing. Our mapped drives still connect and I can
navigate the folders on the sharing pc from any of the other pc's. If one of
our mapped drives should fail I won't be able to re map it. I am trying to
install a program that needs to find the file's om the shared computer but it
can't. All the network settings are still the same.
Can anyone tell me what is goiing on?
Joel