Just wanted to let you all know what I had to do to fix the problem on my 60 gig with the gta iv freeze issue:

I deleted all the stuff I had stored that I did not need and then deleted all gta iv saved data. then did the online system update. I reinstalled the game and have had no freeze issues.

Did you turn of ps2 smoothing off because i was having freezing issues aswell. I turned ps2 smoothing off and it stopped freezing for me wired. I didn't delete anything or reinstall the game just left it as it was..