Killing Floor in game not working

Hello everyone, recently I tried installing KF in my computer, well everything goes well, but once I join a game my mouse and keyboard does not work! I cant move, look around or spectate or even press ESC, this is really odd beucase Ive played KF in this computer before but I dont remember why I unninstalled it. Please if anyone knows how to fix this problem help me, KF is one of my favorite games and my favorite zombie game, so please help if you are a member of Tripwire Interactive or not.