Can see but not access XP computer on network from vista computer

I'm having a lot of trouble with my home network and vista (ironically, I
don't even have to do ANYTHING and it works fine while this computer is
running ubuntu linux :P)

Sharing options are set wide open on the XP computer.

I've installed LLTD on the XP computer, and it shows up in the right place
on the Vista computer's network map, but only the vista computer and the
router show up in the "Network" list window.

Both firewalls are off.

I can successfully ping XP from vista via command line.

Both computers are in the same workgroup.

"Restrict anonymous" is already set to 0 on both.

There is even an account with the same name/password on both.

That last one would be an abysmally stupid requirement anyway, but some
sources say it's needed, and obviously I'm running out suggestions to try
just from searching the web.

So please help me, if you can. Thank you very much.