I'm not sure but I think this is (at least partly) kernel issue. Dimensions of video planes are not handled correctly. They are cropped when rotating (to fit width of 480 in 90 degree mode) but never enlarged. This was done on purpose because initial patches had some issues with video plane when blindly setting 800x480/480x800 dimensions of main framebuffer to planes (because video plane was smaller). I'm not sure this is still the case so maybe the code can be put back? Or maybe not. Or maybe this is something completely different :-)

EDIT: See the original post back then and history around it
http://www.internettablettalk.com/fo...704#post155704