Call Of Duty 4 iw3sp error

Hey Guys ive been trying to play COD4. Now with my computer it runs prefectly fine at very good quality. the only problem i have is that the prologue act and act 1 are fine. but when the last part of act 1 is finished and its loading the next mission as soon as the load gets about 15% in my VisualStudios debugger pops up and the game wont load, yet the video still goes to the very end.
i disabled the just in time debugger to see if it will make a difference and it doesnt.
the iw3sp is the main source of the error,just wondering if anyone has been faced with teh same problem or knows how to fix it.
thanks in advance