PSP sound issue

I installed a 4 GB card in my PSP loaded with music and now my sound is scratchy. When I remove the card and put in the old one, it works fine. I even tried swapping 4 GB cards with my other PSP and still the same. Both cards work good in one PSP and bad in the other. They are both running version 4.01. Any ideas?

Are you sure the card is a sony or is it a fake

I'm 99% sure its sony. I tried another 4gb card from other PSP and still had the same problem.

Thats pretty odd. What firmware version are you running? Also, try using the format utility in the PSP Settings area.