Can't flash firmware!



Hi !
I’ve got a pioneer 105S DVD , which i’ve flashed using a utility called DISC Info 1.5.5
i got to a page containing firmwares for my dvd, so i flashed it , and now it’s recognised as a AOPEN 1640 PRo (!).
I found out these 2 firmware models were quite similar, and the drive works fine
BUT i can’t flash my firmware anymore !!
all i can do is put the current one again
how can i do to get a pioneer firmware back ?