Something has likely got corrupted during the up date - Windows I presume?
Taping the F2 or DEl key sometimes works better than just pressing and holding down. If you still can't get into the BIOS shut down the computer by holding the power button down and unplug all cables. Take the back cover off (see video below) and disconnect the hard drive and take the RAM out. Power on again. This will some times force the BIOS screen to load.
[link|https://www.youtube.com/watch?v=aHbnaAbvbJw|How to open back panel video|new_window=true]
While inside, taking out the BIOS/CMOS coin battery should reset the BIOS to default settings.