Just came back to the forums to give you all the fix for this bug, when you try to start the mission "Momma's Boy" in the Ballad of Gay Tony. I tried all the solutions, turning my graphics down, all of that nonsense... didn't work.
Basically, the solution is: use Fraps to record your game at 30FPS (make sure you select that in the settings), then go and start the mission. It will work no problem at all ! And you can leave your graphics on max, just as they are
The reason I thought of this was that: in the last mission in GTA 4 where Niko wants to kill Pegorino, some people were unable to climb up the helicopter with the space bar.
Someone suggested that the solution was to use Fraps to limit your PC to 30 FPS, so it would be just like the Xbox, where the game was ported from.
Hope this helps people out there looking for the fix!
Edited by Vajayjay, 13 July 2013 - 07:12 PM.