Hit a bug last night where I was locked in the room at the end of the Modrin loyalty quest and 'F' wouldn't work to end it ( I had stayed to hack the console for credits).
I occasionally get stuck floating over environmental objects like rocks and planters, just like in ME1.
The "F" key by defult is the melee button. Did you edit the melee button? If so that is what was wrong. For some reason the programmers got lazy and didn't make it so that the game told you to use the updated buttons. Stuff like this makes me witsh I had just bought this for the 360 instead of the pc. It just feels like a lazy port.