[Scotthall]

I had this EXACT Problem. It is to do with your GTA.EXE. Or in your case the sobiet. Basicly when you edit the handling for the game whether its sobiet or Handling.two file, It will prevent you from being able to push the Attack button. It's something to do with the Nitros etc. I only resolved it with Uninstalling the Handling mods.

Try it and tell me what happens.