The display on my iPhone has stopped changing from vertical to horizontal when I rotate the phone. I only get a vertical display. I have turned the phone off and restarted it, but it makes no difference.
double click the Home button on the bottom, then scroll to the left end of the apps bar. There is where you turn off the orentation to not be portrate mode.
http://www.iphonefaq.org/archives/97974
Good Luck
