Inspiron 6000 screen detected as wrong resolution

I have an Inspiron 6000 with ATI graphics and WSXGA screen. The resolution is 1680 x 1050. Yesterday when I rebooted it, I was greeted with a blank screen. I checked the BIOS screen and it is shifted down by a few inches. The BIOS also shows the screen as "unknown panel" with a resolution of 1680 x 1279. I have a second 6000 with a bad screen so I was able to swap the entire panel assembly as well as the cable. The results are the same on the other computer. What I can't try is the inverter because the bad screen is the lower resolution one. So it seems the EDID is being sent wrong. So what should I check or replace to fix this problem?

Chris