Ok so I was playing Crysis and when I was inside the carrier the game would lag around every corner I took. Im running the game with Very High settings. I opened the console and typed in the r_displayinfo=1 and my FPS was like 45-55. I would watch it and I was lagging even though my FPS was around 45. And I have a 5870, so IDK.
I also just downloaded the Crysis 1.1 patch and it's extremely buggy. the console appears blue and the words flash and stuff. when i go outside the sky flashes blots of blue and yellow and its really annoying, basically unplayable. and i had no problems with the vannila 1.0 version.
Please give us the rest of your specs although it sounds as if your system is short of memory: The lags are caused by the system loading texture data needed for the new scene it is rendering when you turn the corner.
Check in the Control Centre to see how much RAM is available and the Task Manager to see if you have any programs running that might be drawing on system resources.
Take a look at your desktop: Large files or folders there can draw on system memory as well.
Even with the 1.2.1 patch the Carrier is a mess. I just played through it (crashed ever so often, but i made it). It also helps if you turn the graphics settings down to high or Medium (just in that section). You may want to try starting a new career after applying the patch (just to see if the glitches still appear).