Mixed Wireless and Wired Network--Shared Printer access denied

I've read some other posts on similar issues, but I still need to ask for
some assistance. All help is much appreciated.

I am running XP Professional on all three computers in my network. Cable
Modem to Motorola Wireless Router. One desktop PC (Jupiter) has a NIC
connected via cable to that router. One desktop PC (Mars) is connected
wirelessly to that router, and a laptop (Saturn) is also connected wirelessly
to that router. The Network setup wizard was run on all three computers and
all three are part of the same workgroup. File and Printer Sharing is
enabled on all computers in the network. All three machines can readily
access the internet.

Jupiter has a wired printer connected to its USB Port. Mars has a wired
printer connected to its USB Port.

The wireless PC (Mars) can see files on the other two and can access both
shared printers.

The wired machine (Jupiter) cannot see files on either of the wireless
machines. In attempting to explore shared files, a window opens with a logon
screen but my I cannot logon. I am the administrator on all three machines.
I cannot add the Mars printer to either Jupiter or Saturn. Access is denied.

The laptop can see files on Jupiter but not on Mars. The printer attached
to Mars cannot be added to the laptop. Access is denied.

Any thoughts? Thanks again.