I noticed a bug in the PC demo awhile ago. It was at some part (I forget which) where you were supposed to move on, but the enemy keeps attacking if you wait around.
Well, instead of sending more and more Trandoshans, as I guessed it would, or them just stopping (when you killed them all) there was one straggler (shotgun guy I think, no helmet) who would NOT DIE.
My first tip off that something was wrong was that my entire squad was surrounding him and beating on him with the butts of their weapons, kicking him, etc. He wouldn't go down and was continuing to fire his gun.
I came up behind him and jabbed him a few times with my wrist blade, thinking I'd finish him off, but no deal. Eventually my entire squad went down because they were taking damage from his attacks, but he wasn't from theirs.
I then unloaded all my guns into him (even cheated to give myself the guns you don't normally get and used them) and used all my grenades. He killed me at least three times before my squad died, and I revived and tried to kill him for another few minutes. I eventually gave up and just moved on, ignoring him. ; )
I still don't have the full game yet, but hopefully it should come in the mail tomorrow.