My last two companies (a credit card processor and a medical R&D facility) both did criminal background checks and credit checks. Besides the basic recidivism issue, they also want to make sure that you don't have anybody trying to _get you_ to commit a crime. If, either of those companies see too much outstanding debt or a known gambling problem, they might worry that you are dealing with a loan shark, thus organized crime, thus there's a risk of your being coerced to steal some juicy paydata (credit card numbers for the former, new product plans for the latter). If, on the other hand, it's a marijuana charge, there are some areas where they can't hire enough techies if they screen people like you out.
Do whatever you can to convince your future employer that you have no reason to steal from them. If you got grand theft auto for a college joyride, let them know--don't make them guess that you're in organized crime working for a chop shop. If you did get involved with the Mob or something, you're probably out of luck. IT requires that employees have access to juicy data, so it's more uptight than most about things like this.