Dark AleX did a quick hello in their forums, responding to some reported problems with loading PSX games on CFW 5.00. Here's his note:
Some people have noticed an error 0xFFFFFFFF appearing after launching their psx games.
The reason of this is due to some converters like psx2psp are using 32 bits depth when converting the png icon, and new pops only support 24 bits format.
In future versions M33 will check if the depth is invalid, and in that case replace the icon by the dracula one, anyways this is not critical, and an update won't be released only for this.
If you want to make those psx games work in this version, reconvert them using popstation command line tool and using a 80x80 24 bits png icon. Alternativelly if you want to continue using psx2psp and you don0t mind about savedata icon being dracula one, go to options in psx2psp, and in icon0 select "Old default".