Taken from Offcial xbox forums,
A few of you may already be aware, but there are apparently major issues with bugs/freezing/frame rate issues plus more - Rockstar have since made the following statement
"It appears that some older 360s are experiencing frame-rate issues, freezes and other problems. You have our word that we never experienced any of this in QA - in any of our offices or at Microsoft," he stated.
"I am horrified, and we are now working around the clock to rectify this situation. Thanks to Neo-Gaf for bringing this matter to our attention. We love our games and put a huge amount of energy and care into making them all that they can be."