[Macpartners] powerbook screen won't show anything

[arthur steinberg]

occasionally the screen of my powerbook g4, running os X.3.9, won't 
revive when i open it.  the computer is running -- can hear fan, 
hardrive, etc. -- but there are no images.  so i have to shut the 
computer down by simply pressing the on/off button -- not a nice things 
to do since i have occasionally lost things that way.  any suggestions 
of what might be wrong and how to remedy it?

thanks.

arthur