Strange screen orientation problem in N85

Hey guys...My N85 has recently developed a strange issue. The screen orientation is reverse of what it should be naturally. Eg when the main keypad is slid out it should be in portrait mode but it changes to landscape mode, whereas when music keys are slid out it should be in landscape mode but instead it shifts to portrait mode. The problem temporarily goes away when I restart my phone but comes back after some time. Also the higher the humidity level the more quickly the problem recurs after restart. Has anyone else faced a similar issue with N85 or another phone? What do u suggest I do..I don't wanna go to the nokia care as they keep phones for a couple of days