Galaxy S ll gets stuck in landscape from time to time!!! Help!!??

[adil17]

my galaxy s 2 always gets stuck in landscape mode i dont know why, half the day it works well and half the day it messes up bad. evrytime i have to take the battery out and put it back in to fix it. Is this a software or a hardware issue??? I have tried calibrating it, auto-rotate etc but it still doesnt work.?? Please help???!!!!