Hi, I had the same problem while I was running LCPDFR on Vice City Rage. I spent few months looking for threads about this and finally i followed a simple step that worked for me.
First, go to "LaunchGTAIV" application, right click on it and go to it's "properties". Then, go to the "Compatibility" section. There, run the program with compatibility mode for windows 7. Then below that, there is the option to run the program as the administrator, check that box and launch the game. It may not work in the first try but chances of the error not showing will be decreased very much. And also try to load a saved game so when you are playing LCPDFR in the middle and the game crashes, the data gets saved and when you re launch the game it will be loaded with you on the same location where the game last crashed. If you do not have a saved game file then it will crash again and again while trying to restore the crash of LCPDFR. Hope I helped you, Thanks.