[...] Are you by any chance using windowed mode? If so turn it off, see if that helps. I had a similar problem with mouse and keyboard and I just switched back to fullscreen it worked.

So this thing happened yesterday where my TF2 got switched to Portal. (read more about it here) http://forums.steampowered.com/forums/showthread.php?t=3219589 Anyway after I fixed that shit I had to download 6.7 gb of data for TF2 and since that the game sometimes delays my key pressings by several seconds. It usually lasts between 1 and 5 seconds, if I press down a key nothing will happen for a few seconds and then I will move, jump or whatever. Same with shooting but I can move my mouse around and by that I can to some extent "control" my movement. It's really annoying and my friend said that he had the same problem so I was wondering if anyone else has this issue and if they know how to fix it. I haven't tried reinstalling yet because I was hoping there was some easy fix.