i've had the same problem with a debug us ps3, try with ofw 3.55 if it doesn't workfor you try what i did.
first off my problem was it was asking for 3.41 but when it was installing the firmware i kept getting that same error. what i did was when the firmware is gonna install pull the harddrive out before it goes to 1 percent leave the hardrive out till a 60 second timer starts and restarts your ps3
once again it will tell you to press the playstation button
before you press start and select keep your hand on your ps3 controller with one finger on start and one finger on select quickly push your harddrive and quikly press start and select that should bypass it from checking the drive and it installs what ever firmware that is on the usb but wont install any firmware lower than what its asking for.
also this method works for the broken bluray bypass... i've fixed so many ps3 with that method when people turn there ps3s off while trying to update or reinstall firmware. and that's also my method for bypassing blu ray check and returning a debug to retail.
it takes about a couple of trys to get the hang of it it took me a couple of tries before i got the hang of it but once you get the hang of it just pass the knowledge down...
please don't flame this method was posted before but only for loops and i found out myself that it works for , loops , broken bluray bypass, dubug to retail, and when dumbasses accidently turn off there ps while installing or updating firmware..
hope this helped you bud it has helped me a lot...