sorry, i should have mention, yes, also with stock ROM i have this problem.
That's why i think it's the way i use/hold the phone and search for a solution to lock it manual somehow.
I have an Android running too on my device, it runs fine but does have other "problems" like battery consuming for example. Also i have some issues with outlook synchronisation when it comes to contacts and callendar stuff.......
But hey, i serious like Angry Birds.......