Crytek Twitter say's "Please report any bugs at http://gamesas.com", so...

1) Semp Fi or Die cannot be completed. Toward the end of the level, just before you need to defend a crashed helicopter, Delta Squad glitch and lock in place, they won't move toward the helicopter and the subsequent action sequence fails to trigger. You cannot climb up the ledge to the left of the helicopter due to an invisible wall. See http://www.youtube.com/watch?v=QciBjdk3fCQ

2) Semp Fi or Die also contains an irritating sound bug, the line "MOVE UP, GO FORWARD" is repeated over, and over, and over, and over throughout the entire level, even when there are no marines around. See http://www.youtube.com/watch?v=VdP7Gv1EyYU

3) When attempting to crouch and activate the nanosuit menu, the mouse cursor often locks, disallowing the user to click a desired option or to exit the nanosuit.

4) The melee button often stops working, fixed only by a full game restart.

5) Grenade textures sometimes glitch inside grenade caches, appearing in multi-coloured militant-hippy form.

Very strange bugs I have to say. but me , and many people have completed it. So maybe the bug is at yours? Sorry, I cant really discuss about the PC version.

Nope, bugs 1) and 2) are very common. Plenty of people on the Steam forums have mentioned it. It cannon be solved via a save restart or a level restart, and I believe some people have actually tried starting the game from scratch.

I should add, bugs 1 and 2 aren't just experienced by me, people in this thread have the issue, http://forums.steampowered.com/forums/showthread.php?t=1805881&highlight=Semper and this thread http://forums.steampowered.com/forums/showthread.php?t=1806720&highlight=Semper and this thread http://forums.steampowered.com/forums/showthread.php?t=1810028&highlight=Semper and this thread http://uk.gamespot.com/pc/action/crysis-2/show_msgs.php?topic_id=m-1-58608282&pid=960489 and this thread http://www.gamefaqs.com/boards/960489-/58574781 and so forth...