I have a Gemei A330 as well, and also have had that very same problem, minus the firmware problem, which mine is still on the factory set one (1.0).
Anyway, what i discovered was that for some reason, the nand memory cannot handle that many roms for some reason, so i had to narrow it down to a certain number of CPS1, 3D games, NES, SNES, Genesis and GBA roms, slowly chipping away at the number of roms in the game folder, and trying and trying to play them, until it finally worked, and i've had it that way since.
I haven't messed with it since cause the DS R4 cards and other handhelds have captured my attention.
Here are the counts of the roms that i have that are working:
- 3D games ---> 1 ("7 days", no real interest in the others)
- CPS1 ---> 9
- GBA ---> 129
- Genesis ---> 45
- NES ---> 80
- SNES ---> 203
I suspect that it may either be a number of roms or the size of the roms, collective data issue.
As a note, it is possible to run more games off of the memory card slot, which i use to run the CPS2 and NeoGeo roms, the largest of the ones mentioned above.
Hope this helps...