Mouse and keyboard compleatly unresp ...

Here's what happens:
When me and my friend played yesterday over Steam everything was fine for a while untill my mouse and W (forward) key compleatly locked up. My camera started paning upwards and the character only runs forward. I can't do anything after this point, my character just continues running into the wall. In the menu it's a simmilar story, my mouse keeps traveling upwards, but atleast here I can move it around so I can exit the game.
We restarted the server and it worked fine for 2 levels, we were having fun untill it happened again. We restarted, finished a level and in the middle of the next one it happened again. That's when we decided to stop.
Today in the morning I tryed playing by myself and it happened again, except this time it only took a less than a minute to happen. No changed setting helped me and validating the files didn't help at all.
 
This gliotch makes the game compleatly unplayable and it's realy anoying, if anyone has encountered something like this and knows a way to fix it that doesn't involve deleting and re-instaling the game I would be realy gratefull.