Fn key lock BIOS setting indifferent

Hi, I have a Precision 7510 but it's not a choice as a category so I picked Latitude for this question. My Fn key is locked and I've read everything there is to know about it on the web but it doesn't solve my problem. No, Fn/Esc or Fn/NumLock and other shortcuts don't work. The BIOS setting is supposed to release the Fn Lock, it's in the POST settings in my BIOS (v. 1.19) but it doesn't work. Whatever I chose the Fn key is always locked as depressed. I've tried rolling back to 1.0 but it didn't help. I've checked the keyboard connectors, they seem good. The keyboard seems to work since all Fn combinations work without having to depress the Fn key. It's not Windows because the problem exists in BIOS already: the arrows don't work there because it probably detects Fn/arrow. Please help, I'm desperate right now, don't know what to do... Thanks

Cheers,

Guillaume

PS: maybe the keyboard itself but I never used the Fn key, strange that it would fail... ! Anyway to deactivate it cutting a wire ? I don't need it...