Does your memory card still work on the PSP if so "logically"format the mem stick back up the rest of your files on cpu use a format program you would use for makin a pandoras battery or run format memory stick under system settings. I had a mem car that when I try to load anything on a mem card it would freeze and shut down and if I try and delete via PSP system settings format it would freeze and shut down AND if I try and delete via cpu it gives me the same error msg I had to get a new 4gb.
rep + if it worked for you