hmm, if its a complete system freeze rather than just a application crash then maybe your cpu is overheating? I've had this problem when my fan got bunged up with dust. Games would freeze after 20-30 minutes of play. You could try checking your system temperatures in one of the many free programs such as realtemps. Other than that, hacks can break games so try not to use them for that reason if not on principle.
also, is your copy of batman legit? I wouldn't ask but I heard that the developers had filled it full of hooks (code that makes a pirated game unplayable) .