Correct me if I am wrong, but the first time this really happened was on GTA IV. You had codes such as '359-555-0100' which gave you an Annihilator helicopter but blocked achievements such as One Man Army; Survive a 6-star wanted level for 5 minutes and Walk Free; Escape a 4-star wanted level. However, if you had the brains about you, you would have your main account with cheats and a little side account for doing the achievements that were locked when you entered the cheats. So, if you can do this, why do they lock them in the first place? If it is to stop you using cheats, why not not put them in? Think next time developers, thanks, lwilson014