Try Koda's flash tool mate, it worked fab for me with the P5Q Dlx... link here : Koda's Asus bios tool

Follow the instructions, you need a good USB key ( at least 512mb) but it works amasingly...

Current P5K dlx biosses via the tool :

P5K Deluxe WIFI-AP

Bios 0902, 0812, 0809, 0705, 0703, 0603, 0601, 0404, 0311, 0202