Mumble overlay stopping games from launching

[mashinu]

None of my games will launch when the mumble overlay is turned on, Steam will say I'm in-game for ~5 seconds, then goes back to saying I'm online.

When the overlay is off the game runs fine.

My video card drivers are up to date, I have also tried re-installing Mumble

this seems to happen with most of my games, oddly with the exception of older ones like morrowind and thief.

When running Crysis 2 with the overlay on, I got this message:

http://i.imgur.com/ayTEJFE.png

The message does not appear when the overlay is off.

Some additional information that might be helpful: I had to re-install windows 7 a while back, and manually installed drivers for the computer. Also iirc this problem first occurred when I was working with OBS (Open Broadcaster Software) and its game capture recording mode.

Can anyone make sense of this?