Vista machine visible but not accessible

I have a home network with 2 vista machines and 1 XP machine. Until recently
all was well. I could access everything from every PC. Now from my main
machine Vista Ultimate 64 I can see Vista Home Premium machine and can access
it's shares, I can not see XP Machine. From Vista Home Premium I can see
Vista Ultimate but no access is allowed (Error "Windows cannot access
\\ultimate....check spelling of name, maybe network error.....etc) Although I
am clicking on the icon in networking for that particular PC I still get this
error. Anyway from Home Premium I can access XP. From XP I can access Home
Premium, I can ping Ultimate, but cannot access it via \\ultimate or
\\192.168.1.x. This result is the same with or without the firewall on Vista
Ultimate.

Now if I type \\xp then I get "Windows cannot access \\xp.... Check spelling
of the name.....etc" When I click Diagnose it is telling me a cable is not
plugged into the network adapter "Local Area Connection 2". Funny thing is I
am using Local Area Connection for my network access, Local Area Connection 2
is my bluetooth adaptor. Any ideas?