PSP can't read the memory stick

Hi
I have a phat psp with the 3.90 m33.
Yesterday, I copied a psx game to my psp, but since I didn't know in which folder I should put it in, I copied it to the ISO folder. After that, I wanted to play something and then the menu gets all wierd so i decided to format de memory stick. However, after the format, the psp says it can't read the memory stick and that I should format it, but when i do it the psp says there's no ms inserted.
I've already tried to format the ms directly with a pc and formated flash1 with the recovery menu.
Please, help this noob.

You might want to try:
Patch to Load 3.71 fatmsmod on 3.80/3.90 M33 Version 2

If you have Pandora UPMS can put it on and take it off