FUCK YEAH!
It's working again.

I've posted threads about this on four forums, but no one could help me. Therefore I had to try to fix it by my self, and so I did. If anyone ever gets this problem, this is what you shoud do:
Go to "Options" and "Preferences". Then you go check the audio device, and change it. For me it was on "Microsoft Sound Mapper", but to make Vegas work I had to change it to "Windows Classic Wave Driver".
Well, thanks anyway.