Why dont my cheats work for vampire bloodlines?

Okay. for my game the mascurade (sp) bloodlines i have the cheats on and everything but once i activate them in gameplay my game freezes. now i dont know if it is just taking a long time or isnt working at all but i cant put cheats on without the game messing up. Someone tell me how i can fix this or am i just screwed. please and thank you.