Accessing Network Folders

I have a central XP Pro based machine that I use as a HTPC and media server.
The machine runs BeyondTV and hosts my music collection. I also have a XBOX
360, so I used Media Connect 2.0 to allow it to access the music.

One a second machine I've installed Vista Pre-RC1 to mostly checkout how
well MCE works with a TV tuner, but due to HDD space issues, I'm keeping the
music on my HTPC. When I look at the network in Vista, I can see the shared
MC2.0 content but I can't access my music share.

I can access the TV recordings share through the Network folder on Vista and
directly through \\HTPC\Media but when I try the same using \\HTPC\Music I'm
given an access error.

I can't seem to get around this error. My laptop, 360 and another desktop
machine can all easily access the music folder share.

Any ideas?

Thanks.