Psp cfw 5.50 problem?

hi i have cfw 5.50 and i cant star any games it says file corrupted cant be star but the file is not corrupted i use to have 5.50gen-d ive changed it 5.50 and all messed up please guys help me tell me what to do i cant tart any psp games from my memory stick i don't know what to do about this