T500 came with a 16:10 display or 1920x1200.
T510/20/20 came with a 16:9 display or 1920x1080.
Are you sure that when you replaced the CMOS battery you didn't knock something when you opened it.
I found other CS09 machines to be fine. Never had an issue on any of my T420, T430s, or T520 units.