Could a self save from premiere cause the problem? By this i don't mean the autosave.
Autosave is the only kind of 'self save', and is not likely to 'cause' project corruption.
thnx for your reply. My first question came from a remark of Gakhue:
"I'm using CS6 and I got that warning, I copied my project file on usb stick and re-opened in a different computer using CS5, it then gave me a few warnings about changing the name and saving it to auto save fault, I clicked away and said yes to each one"
So i wondered how he did it 
The second question came from the fact that my last save was from 17 minutes after i left my studio. And i am not talking about an autosave. It was the main save of the corrupted videofile. And since i did not do it myself, the only option left is that Premiere did it? Or that premiere does not use the internal Mac clock and is on a different time. Which is not the case (just tested).