I just came back to the office after being away for a month, plugged my mac into the 30" Dell display I have at work (rotated 90 degrees), and it the resolution is now 1536x2048 and that is the highest resolution available in System Preferences. Before I went away, I was always using 1600x2560, which is the native resolution.
If I remove the "90 degrees" rotation, it will let me use 2560x1600, but changing it back to 90 degrees drops the resolution back to 1536x2048.
The only thing I changed while away was upgrade from OS X 10.7.2 to 10.7.3. Perhaps this was the problem?
How can I change it back to 1600x2560?