Access Denied, XP Pro, SP2, Peer to Peer LAN

Running Win XP pro SP2 on 4 machines,,, peer to peer LAN (workgroup)
My problem is, I can not connect to any of the shared folders I’ve created
on one of the machines from any of the other machines. Each machine can open
any of the default Shared Doc folders for each of the users of all the
machines. The machine that will not grant permission to view (open) any of
its folders I have shared on the network can view (open) all the shared
folders on all of the other machines.
I first noticed the problem after installing a second license of QBooks on
one of the machines. When trying to point QB’s to the company files on the
host machine I’d get this,,,,
””” \\ blah blah\shared folder name is not accessible. You might not have
permission to use this network resource. Contact the admin of this server to
find out if you have access permissions…. Access is denied””””

Also,,, not sure if this has anything to do with it, but,,, the machine with
the second seat of QB, in the My Network Places folder is listing all the
shared folders not on that machine as located on The Internet and not on the
Local Network as it should,,,,,,,, Man am I confused!!!!!!!