N80 Joystick left fault

I've just got a new N80 but I have a fault with it and was wondering if it was perhaps a common fault. At some random point the phone seems to think that the left position of the joystick position is constantly pressed. It happened for the first time last night and annoyed me no end! Eventually I gave up trying to get it to work properly and just went to sleep. In the morning I thought I'd have another play and it worked normally! I hadn't switched it off or anything! When it was malfunctioning I tried taking the battery out etc but it didn't fix it. Now tonight after playing with it all day, it's suddenly decided to do it again!

Any thoughts :???: ?

Thanks

Akira