There is a huge bug with Wheatley's rage. Once he raged he can't place the sentry or any any buildings on the PDA. When he has raged he can't attack unless you use mouse wheel to change to the gunslinger (which alot of people don't know).

Oh i thought im the only one with this Bug because i can't switch weapons with the Mouse wheel (its broken). but if you have it too with a normal mouse then it must be a realy Huge bug.

I noticed that too. When I was wheatley I was trying to find a safe area to put down a sentry and I pissed off about it quite a bit and if remember i lost because of that. XD