When my 64GB Playbook wakes up from standby, the password screen will sometimes be upside down. Just holding the unit vertical will not reorient the screen. If I rotate the unit several times eventually the screen will present the password screen right side up.
Just a symptom of age as the Playbook gets older (had it for three years now) and the orientation sensor ages? The orientation lock is normally off since I sometimes need to use the unit in vertical mode.