Have no idea why this started or what is causing it. I have an iPhone4, JB and unlocked on 4.0.1 using Greenpoison. For some unexplainable reason, at least 10 times a day, the phone will short vibrate twice, and the sounds change to default, the screen brightness goes to default, and a few times a day, the icons go from 1 home screen with nice folders to spreading out over 4 home screens. Anything can trigger it - SMS, Calendar alert, phone call. I don't have any unusual apps - notifier, multiflow, folder enhancer etc.
I can always restore to 4.01 and jailbreak again, but didn't know if any one else had this issue and a fix or if it may be a specific app that was updated to 4.2.1 that may be causing this to happen on my 4.0.1.