When using package midi-res, the whole psp locks up when a game is ended and the new one is loaded from AMS. Occurs randomly with every game. When the sounds are loaded from the memorystick, the psp locks up totally. It's not yet solved in 0.5.4 final.
There're 2 midi-res packages: one is ~1.1MB and another is ~14.8MB. Which one are you using to reproduce this bug? Thanks.