I see there's a lot of reported problems with getting the game to launch, but I've yet to see anyone bring up the Steam version. I'm on Windows XP SP3 right now (I'm dual-booting on an Imac, and I've yet to try downloading the Mac version of the game) and after I click play, it seems fine for a second. The screen turns black, the flux capacitor comes up and fluxes, music plays for a brief second...and then it just freezes until I bring up the task manager. I've tried re-downloading it with no luck.
Episode 1 still works fine, so I know it's just a problem with this episode. I'll go see if the Mac version works and let you guys know how that goes. In the meantime, any help would be welcome.
EDIT: Mac version is working fine, at least.