[dtndvm]

Definitely should not do that. Try soft resetting first. If that doesn't help, go into settings\system\G-sensor and try calibrating the sensor (shouldn't matter because the keyboard should override the sensor...but can't hurt). If you haven't done any registry edits or installed anything like Gyrator that messes with the screen rotation, you may need to hard reset to correct it. If you've installed any app that changes the screen rotation, uninstall and soft reset.

If it persists after a hard reset, take it back.