I reinstalled JO, and there's a cyclic redundancy error when it gets to assets0.pk3! plz help!
clean your CD, and if its scratched badly, you may have to get a new one.
Fanbill is right on the money.
I had this exact problem two weeks ago when reinstalling JK2.
All I had to do was rub the cd on my sweatshirt a little bit.
It's totally a CD scratch/read problem.
Back-up the cds or buy 10 extras for emergency :D
Use a virtual drive. Its very handy.