Access denied to XP from Vista, but ok to Vista from XP - HELP!

Apparently this is an ongoing problem for a lot of people. Unfortuantely I am
having the same issues:

I have 1 XP machine and 1 Vista Machine.

I can see and access all shared folders and files on the Vista machine from
the XP machine.

I can see the folders shared on the XP machine from the Vista machine, but
cannot access them or the files contiined therein. I get a long error that
finishes with "Not enough server storage is available to process this
command."

Both PC's are connected to a router. Both are set up for the same network. I
have installed the patch for SP2 (KB922120) on the XP machine and have
ensured the ports under Windows Firewall for File and printer sharing are
enabled and list the IP addresses for both machines on the XP machine.

Phone calls to both HP and Microsoft end up with, "we can't help you with
this problem unless you pay out the nose for it." Hopefully someone who has
experienced this problem already can help.

Chuck, I have been all over your Blog website, but just getconfused with all
of theinfo there. I'm sure have some great iinfo, but I'm not computer savvy
enough to get it.

I need step-by step instructions, if possible, to check and set the
appropriate settings. Please help!

Thanks!
Storbought