I am suffering from the same problem. I purchased a PS3 Key unaware of the fact it will not jailbreak my system running 3.55. It seems as if I am just screwed unless I return the system and try to find another 320 GB console that hasn't been upgraded to 3.5 yet.
My (most likely painfully nieve and novice) inquiry is "Will Restoring your PS3 result in the downgrade of the system version back to the version it came with out-of-box?" I already seriously doubt it. If not, what can be done to take my firmware version from 3.55 back to 3.41 so that I can use the PS3 Key I recently purchased. Any help will be greatly appreciated.
Unfortunately, you're out of luck! There is one obvious thing you need to hurdle, 3.55 firmware. And since your console is newly purchased, you might also want to check if the model is CECH-251x. If it is, that's another thing you'll have to worry as per experiences of many. They say models with 251x cannot be downgraded while those with 250x and below are still capable.
For now, that's where you are but who knows right? Things have been moving faster now in the PS3 homebrew scene. It's just a matter of time.. I suggest holding off any updates in the meantime.
Im stuck in factory/service mode im using E3 card reader.. and i downloaded the modified 4.31(PS3UPDAT.PUP) file and the 1st file(Lv2diag.self) and put in my 16 gb flash drive (FAT32) but everytime i turned on my ps3 nothing happens. I did put the flash drive in the right most slot in my ps3.. and I have CECH-2001A serial.. need help pls.