I have the Logitech diNovo Bluetooth keyboard. It works great with Linux, and works in Grub, in my BIOS, and everywhere else.
Is your bluetooth keyboard interacting via a USB-based Bluetooth hub? Which keyboard are you using?
Key (for anything using a USB-based bluetooth hub) is to jump into the bios and select "Enable USB Keyboard support" (howto depends on your bios...)
I'm now in the process of fully enabling all the bluetooth support within linux, so that I can use the extra buttons on the keyboard, my bluetooth mouse, and my media pad. This link is pretty helpful along those lines: