Could be too many apps running(not enough free ram)? IOS4 is Ram hungry like a bloated Windows PC. hence it comes with 512MB's of Ram. I run it on my 16gb 3G with Multi tasking and Home Screen wallpaper. I try not to run too many memory hungry apps at the same time and usually "close" an app after leaving it vs "backgrounding" it. I can live with it for now or until I can find a iPhone 4. I did this not by choice. I had a major crash and couldn't not recover from backup. I had to "restore/ upgrade" or my phone would be "bricked" A lot of the apps I used on JB 3.13 don't work/ crash on IOS4 ...I really miss Wifi Sync. Quick Lock