Always make your own Trouble Topic unless your system and setup Matchs the other players, which yours doesn't. (Disc vs. Steam)
Have you tried the delete GTA_SA.file? reboot and play.
Did you Mod the game in any way?
Did you use any Cheat and save?
What is your OS?
How much of the Game (last mission) did you play before the problem.
Are the Saves your own?