New networking problems!

I've had a wireless network working (almost) flawlessly for a long time
but, all of a sudden, I can't connect to the drives on my other computer
from my main computer. I can ping the other computer and I can connect to
the drives on this computer from the other one.

Here's what I've seen so far:

The drives on the other computer keep reverting back to $C on the 'share'
screen.
When I try to map a network drive on this computer, the other computer's
name comes up in the WORKGROUP list but not the individual drives (that used
to be shared).
When I try to access those drives using "My Network Places", I'm asked for
a password. My hotmail name is already filled in but grayed and there are
not other choices in the drop-down menu. I tried accessing using my hotmail
password but that didn't work.

I'm at my wit's end and I don't even know how or why this happened.
Anyone?????

--
Nadyne Nelson
(E-Mail Removed)