Actually the balck screen is not necessarily anything at all to do with anything other than FPSC so dont just assume that Windows has crashed.
Running my MP games over LAN (dont play over the web) I have a black screen (both machines) while windows ceases to function though theres not a thing wrong with it - patience is required as FPSC takes over your environment while it does what it does (not even Lee knows what) in apparently waiting or seaching for - again who knows what before it decides its waited long enough and loads the game quite perfectly as it should after wait for it - 10 minutes of nothing more than the balck screen. At the time of waiting at the black screen not even the windows clock will work - Windows itself freezes - but comes back to lifs as soon as FPSC has done what it needs to and loads the game. FPSC just takes over while loading and grabs all the cpu time effectively disabling Windows and everything else.
Thats my MP games. Works perfectly but just takes the 10 minutes to load in both server and the joining machine.
Just go make a cup of tea while you wait.
Mind you you could be waiting forever - but thats how it works with me.
No other probs just a 10 minute wait.
Nothing wrong with that you might say - even a one level of an SP game takes 5 minutes to load with me and I have big systems so I guess in terms of wait time when you are talking FPSC anything can happen and usually does.
I would suggest the original poster give it some time before deciding to exit and see what happens.
Of course nothing may happen no matter how long you wait but its worth a try before ruling out FPSC is just working away trying to load the game.