I can't complete the last level. Not because I'm crap (Although that is highly debatable), but because it crashes every single time I fight the last boss. You know, that enormous robot alien dude? I fight him, and within a minute the game crashes unexpectedly. I tried playing it with every setting turned all the way down, to no effect. It still kept crashing.

This happening to anyone else?

I remember falling through the ground a few times, only to end up stuck in the sky.

I tried it again with my settings tweaked and I didn't have any more trouble.

First time I tried to beat the game it crashed on me and I was really upset about it because it crashed after I beat the game and the final cinematic was playing.  I would have to say, patch first and play a save point before the boss fight.  You might have to fight him again and even after he is beaten, you have to be aware that it could crash at that time too as any object could unexpectedly kill you.  I know it's strange and very inconvenient but eventually I managed to get through it.  

Crysis is buggy  played in vista under dx10 ,,, go to vista games icon on start menu, right click the crysis icon select play in DX9 ... ALL PROBLEMS SOLVED. game will run smoother all round and NO crashes.

I know this topic is old... but anyway, if anybody has problem with game crashing on last boss, it happens under Windows 7, osmething to do with dx10, as said above, switch to dx9 and it will run. 
Under Vista there should be no problem even in dx10.