Have you changed your game kernel to 1.50 in your recovery mode? (turn off psp then turn back on holding R bumper)

Sometimes installing an earlier version of scummvm will work.

Unfortunately, you also have one of the worst firmwares (in terms of functionality) available for the PSP. In efforts to thwart users from using bootleg copies of PSP games, Sony downgraded the speed at which your PSP will read from memory stick (b/c most hackers load games off of the memory stick)....