Thanks to everyone for this very useful thread.

Had the same problem on my Acer Aspire 5630. Only 1024x768 area of the
1280x800 display was useable, with a wide black margin on the right and
an area at the bottom where the last row of the display is stretched
down to the bottom of the screen.

After seeing this thread, I bought a second hand cable off ebay (3.50
GBP delivered - bargain!). Changing the cable has solved the problem,
and the display now works correctly.

New cable was advertised as coming from an Acer Aspire 5680, but it had
the same text on the label:
HBL51/HBL50 15.4" WXGA
DC020007O00
MEC REV: 2.1

I unpicked the tape from the faulty cable and found a broken yellow
wire, right where the cable bends in the hinge as you would expect.

Thanks again - laptop is now fixed for minimal cost.