I had San Andreas. I hated it, and thank god a local pawn shop gave me full price for it. I bought Hearts of Iron 2!
Anyways, I ran the cracks prefectly back in the day (2 weeks ago
). Your DVD must be damaged in some way, because that is the weirdest problem I have ever heard of. Cracks usually don't mess with the original DVD, and if that IS the case, you may just want to uninstall/reinstall San Andreas, and use the original.
If the original is damaged, Rockstar will take it back and send you a new one. Lemme know if you need contact information for them.
Edit: Never try to run SA without the patch. There's SERIOUS flaws in the PC version in 1.0, graphic coding being a major one.