three options
lcd screen defective
cable damage or bad connection
videoboard defective
the easy test to isolate to solution
check this through attaching an external display
if the external display shows up fine, the videoboard is okay
be ware of display resoltion settings, witch could mislead your results
that leaves us to lcd defect, or bad cable, cable connection
if you are a handy, dismantel the machine
check the videocable, it might be damaged in the hinge
or have come loose at connectors through the fall
at last, replace the lcd screen
get a second hand one from ebay
Jeroen van Putten, November 2008