Random coloured pixels

I haven't used my PSP for a while because of this rather annoying error. However, I'll try remember the details of the error.

It seems to only happen during emulation of PS1 games. The game will last a few minutes without a problem, but randomly during gameplay, pixels on the screen change colour completely. They are usually pink, yellow, blue and green. It doesn't seem to be related to the scenery in any way, just random colours in general. There are HUNDREDS of them, some times even taking the full screen. So...what's up?

Sounds like a corrupted ISO image. Maybe. Try compressing it less when you make the EBOOT.