For the unluck few who upgraded to ofw 5.50. A ray of hope.

Seems to be a rumor but it's not been proven fake or otherwise. So i
thought of posting about it. Looks like a German user Miche2245 has
found a save game vulnerability in Firmware 5.50. Apparently Monster
Hunter Portable 2 (JAP) and Need for Speed: Underground (ENG) are the
only reported UMD games to be working at this stage with the save game
exploit.

If you are on OFW 5.50 and have Need for Speed: Underground English
UMD, why not download the exploit and give it a go? Once the exploit
works (if it works) You can then load upChickHEN R2and Custom Firmware
Enabler 3.5. After all that work make sure you just put your PSP into
standby mode. Oh and do comment back with some solid proof that this
works!

http://pspslimhacks.com/downloads/cfw/savegame_exploit_5.50.rar

Do it at your own risk