After a large amount of time testing and retesting, I have come to the conclusion that the official 3.50 PSP Firmware update and the 350 Lumines HEN and Downgrader can not co-exist. If anyone can find a workaround for this, it would be great.
Now before you start telling me that it isn't necessary because of Pandora's battery, this is why I need it.
I have a 1gb memory stick and have made it into a Pandora's stick. It works great, but has a lot of wasted space. So I want to make a universal stick. With my PSP, I carry around my Lumines disk in the drive, and my Pandora's battery with Booster's normal boot loader for it, so I always have a Pandora's battery with me. I carry my 1gb magic stick in my case. I want to be able to upgrade any PSP to 3.50 and downgrade it with the Lumines exploit, or have the option to flash 1.50 with Pandora's battery. I also downgraded my PSP to 1.50 and added Dark_AleX's POC firmware and made a NAND Dump of it and renamed it so it could be flashed. So if I am out and about, I will have with me, all the tools to downgrade any PSP and update it to 3.52 M33-4 (Both the installer and -4 update are on the stick) or 3.40 OE-A (also on the stick with data.dxar already made) or keep it at original 1.50, or with Dax's POC firmware.
From what I can tell, both the official 350 update and the 350 downgrader must be placed in the PSP/GAME/UPDATE folder to be recognized by the firmware otherwise be subject to the corrupt data icon. I do not know why this is, or if there is a way I can modify the EBOOT to make it work, but I have tested it many many times. Does anyone have any suggestions?