By any chance did you increase the medication in the inventory using the cheat beyond what it should be, it should be either 1 or a 2. anymore than that then game lock up with the shady guy.
The game doesn't like when you increase items beyond what they're designed for, you need to keep them at the level they're intended, anymore then it can break the game, like what happened with the shady guy.
Same goes if you increase relationship points beyond what they should be at each step, you can miss trigger and as a result miss scene, which could result in not being able to progress in the game.