MSN Messenger Webcam trouble

me webcam was working fine yesterday and so was my friend's but now when i try to start a video conversation or send my webcam it wont work! I havent changed any settings, his wont connect but if we go into windows messenger his does connect and when i go thru the audio tuning wizard it says my webcam isnt working properly may be in use by another program but there are no other programs open for that to happen. Can someone explain how to fix this please