Firstly, this is not for the 60GB PlayStation 3's, some of which freeze up at the beginning of the game. This is for those with a 40GB console whose game often freeze up, particularly during missions.
Yesterday I connected my PlayStation Network ID to the [Register or Login to view links], ever since then my console often started with a temporary 2 - 3 second freeze when I load up my game, then luckily the game continues. But when I started with missions today my console constantly froze up at certain points, specifically at the start or end of missions.
I reset my console multiple times, yet the problem still continued. I read that others were having a similar problem, so I knew I wasn't alone. Then I thought about signing out the PlayStation Network, and for hours of playing after that the game has not frozen up once!
I then scouted the message boards and found that this particular solution completely works for other people as well. So if you're experiencing the same problem, try this as well... it definitely is a better solution than the one Take-Two offers - deleting your save game!
Apparently it has to do with the game having trouble sending your statistics to the social club server. Hopefully Rockstar Games and Sony will find a solution to this.