Networking Problem

I currently have three XP (P3) machines networked together via CAT5 to
a wireless router. I call them machine-1, machine-2 and machine-3.
All are in Workgroup 'MYHOME'. All folders & files on all 3 machines
are set to file sharing, allowing all user mods to same.

'My Network Places' on machine-1 shows all content of machine-2, and
allows accessing/changing to same. It does NOT show machine-3 at all.

'My Network Places' on machine-2 shows all content of machine-2 &
machine-3, and allows accessing/changing to same. This is as it
should be.

'My Network Places' on machine-3 shows all content of machine-1 &
machine-2, and allows accessing/changing to same. This is as it
should be.

So, basically, my problem is that I cannot access the content of
machine-3 from machine-1, and I cannot figure out why not. I have
tried several things - to no avail. It seems strange to me that
machine-3 seems set up correctly enough to link both ways with
machine-2, but only one way with machine-1. Otherwise, my network
seems to work fine.

Looking for help.

Thanks

Frederick