This happened to my old Compaq Armada, and in my case it was the ribbon cable. No idea of cost as it was fixed by my work IS department cannibalizing another machine of the same model that had been pensioned off.
For the record it also happened to the fold out screen on my three year old Sony HDD camcorder a few months ago, and my parents' two year old camcorder from the same Sony product range too a few weeks later. In both these cases the cause was also ribbon cable failure. FWIW fitted replacement cost from a repair shop I found via Google search was about seventy quid.