Are there any known LAN problems with Vista?
I can play online with no problems, host and joining fine, but recently me and some friends had a LAN party, and EVERYONE but me had no problems creating or joining LAN games.

I get "Connection Failed" or "Connection Lost" whenever I try to go Multiplayer -> LAN; as in, just trying to go INTO the LAN section, I get that error (from the main menu!!). If I keep clicking, EVENTUALLY it'll let me in.
Once I get in, if I try to host a game, same problem (except no matter how many time I try, it never hosts).
As for joining, 9 out of 10 times, it will forever sit at the "Joining Game..." part. Forcing me to minimise it, kill the process, and try again. However that 1 out of 10 times will work perfectly and it will load in and play like normal.

What I'm confused at, is why on earth it says "Connection Failed" or "Connection Lost" when I just try to get into the LAN menu! Not even trying to join or host (sometimes I don't even get that far!). This is really bazaar.
I'm going to try and install XP and see if it fixes the problem, but from what I've generally seen, no one has had a similar issue in Vista (at least I couldn't find any).

Running: Vista Ultimate x64, Leadtek GF 9800GTX, Xeon X3350 (<- btw this "fails" the minimum requirements, lol), 4GB Coarsair Dominator, all latest driver, etc.

Any input would be greatly appreciated.