Acessing computers

I just got a new computer and installed my mn-500
wireless base station to it. Yesterday, all computers
were fine, working, on the network, online and could
acess the files of each computer from all the others.
Today, the new computer says that it cannot find the
network path for any of the other computers on my
network. The other computers cannot acess files on the
new computer either. However, the new computer is online,
and it shows up on network places on the other computers
and in the networking utility, it picks up both of the
other computers. Why can't i acess this new computer from
other computers? Why can't i acess other computers from
this new one? Thank you for your help.