What sort of scratches are they? If they circular scratches (i.e. ones that run in the same direction as the disc spins) than those are much more likely to cause read errors because the scratches run in the direction that the laser reads in.

I once had my copy of Super Mario Galaxy scratched by my Wii. Luckily Nintendo replaced the disc free of charge.

__________________
United by the gods, we sail the violent waters
They gave us a sign, a man on a cross
Supposed to save us all, but their minds are forever lost..

"Back to North" - Merciless

"If you're wondering how he eats and breathes / And other science facts / Then repeat to yourself 'It's just a show, / I should really just relax.'"