Your title mentions a problem with the bios, your text mentions a problem with the boot menu.
Which is it that has the problem?
If it is the bios then it has nothing to do with Mint because Mint hasn't even started to boot at the time you access the bios. If it is indeed the boot menu which you can't access then the next question would be, is Mint the only distro on the machine? If so, you don't even need to see a boot menu, set the GRUB_TIMEOUT value to zero in /etc/default/grub. Of course that is not a fix, just a workround and only works if you don't have to boot other distros on the same machine.
Fujitsu Lifebook AH532. Intel i5 processor, 6Gb ram, Intel HD3000 graphics, Intel Audio/wifi. Realtek RTL8111/8168B Ethernet.Lubuntu 13.10,Ubuntu12.10 (Unity), Mint16 (Cinnamon), Manjaro (Xfce).