I managed to brick my Gp2x beyond repair when I tried to install the firmware upgrade. I got the ‘upgrading firmware’ screen for 15 minutes, followed by a black screen with nothing happening for 10 minutes. At that point, I reset it & got a white screen. It looks like the boot loader was damaged, since I don’t even get the initial black logo screen. I tried the unbrick most gp2x procedure with no luck.
I see that the SD card I was using was formatted FAT16 rather than FAT32 which is preferable. Maybe that’s why the flashing failed.