I just had the same blank screen problem, but you can get your machine to work
if you plug into a flat screen monitor (not a CRT) and FNC + F3, and that toggles to
alternate monitor (your flat panel) so at least you can use your machine till it is fixed.
I contacted HP about the problem, and they said the Display Card is bad.
But check when booting-up to see if you get clock error 0207 which means your
battery is dead, and may keep the monitor from sync with CPU.