iphone 4 icons won't stay on second home screen

I've moved the icons and folders for my iPhone 4 to the second home screen so that the photo I use for wallpaper is unubstructed. When I turn my phone on in the morning after being off all night, the icons have moved back to the first home screen.

This began after upgrading to IOS 5. It doesn't seem to happen each time, however. I upgraded on Wednesday night and I guess it's happened three days since.

Any ideas on how to get them to stay permanently?

Thanks