u didn't mention whether u r trying to copy the NTSC or PAL version but if you are copying the PAL version this is the patch you need:

You can get it from: http://www.megagames.com/psx/psx_patches_c.shtml

and the patch you are after from the list is:
Crash Team Racing Protection Fix EURO PAL 327KB PDX

I know for sure that this patch works with the UK version since this is the exact patch that i used.

Applied it using PPF-O-MATIC and CDRWIN on a memorex 80 minute disc and ran it on a standard psx with a stealth modchip. It works fine.

So try using this patch and see whether it works. If that fails get some 80 minute memorex discs from www.jungle.com and if that fails then it could be your modchip, but i doubt it.

hope that helps,

Animal.