Damn Helicopters with their mounted guns!

I skipped the gym yesterday on account of feeling a little tired from the SoS weekend. Katy was too tired to come around after her LRP so I took advantage of some me time to carry on with a few levels of Far Cry (I'm somewhere around "Archive"). I took me a while to realise the reason I was getting the crap shot out of me was because the mutant bad guys where invisible up until they start ripping you apart

with their bare hands! I eventually finished playing after a couple of hours as I'd reached a level where the helicopter with the mounted chain gun keeps killing me despite the fact I totally blew it up with the rocket launcher. Its either a bug or a scripted part of the game.

Ug, plot on rails anyone?