From Kotaku about today's 4.45 firmware update for PS3:

"We've started getting reports from some readers that the update is bricking their system, locking their consoles on the boot-up "ribbon" screen, and a thread on Sony's official forums shows the issue is far from isolated."-Kotaku

The odd thing is this isn't effecting every PS3. I've updated my old 80 gig console and it works fine but still be very careful and watch Sony's PS Support Page for updates on the situtation. Till then, avoid updating until the problem is fixed.