(Spoiler) Have a bug related problem with Crysis.

This may be considered a spoiler.

I'm at the very end of Crysis, single player, and the Tac Gun will not lock onto the big spaceship, I have been reading that it is a bug. Is there a way around it?

Did you blow open the underside with rockets and the gauss rifle?

That doesn't seem to have any effect. The woman in the aircraft keeps telling me to lock onto the cannon.

She means destroy the turrets. Then you use the gun to blow up the huge cannons. Unless you did that, in which case I recommend going to an earlier save.

I got the turrets. I read of someone else who had the same problem and he restarted the game just before you have to collect the TAC Gun. I was just wondering there was another way around the problem.

lol the first time i went through i forgot to grab the tac and if you go on the deck you cant get back down to get it. She was like "use the tac cannon" for several minutes before i finally realized what she was talkin about. Make sure u lock on to the arms or whatever, they are on the sides of the ship. Run around till u can get a clear view

*****Spoilers*****

There are two turrets. I guess you got those.
The center of the ship has a circular hatch that opens and closes. You need to blow open the doors using whatever conventional weapons you like. Once the door is open the TAC gun should lock onto the ship when you point it at the hole.

This did not happen for me first time either. I was playing at high graphics. The next time I played I dropped down to medium but I think medium shaders should be good enough. Playing at medium the final part went without a problem.
There were other glitches like clipping through walls in the alien ship when I used high graphics as well.
I figured a C2D @4 GHz and a 8800 GTX would be good enough for high DX9 but I guess not.

I played most of the game at medium settings and it went fine till Paradise Lost, the flying aliens really started slowing things down. I had to drop the graphics to low settings and it ran smoothly, one or two glitches but nothing that made it totally unplayable.

It's not a bad game. I've also been playing COD4.
Am I getting better at these games or are they getting shorter?

I just replayed the last section and I managed to get a lock on the first cannon but not the second!!! I give up - the aliens win, for now....