I have an iPhone 4 on order, but I upgraded my 3GS to iOS4 earlier today to try it out. Ever since then, I cannot get any sort of data connection over 3G. I am showing full 3G signal, but no Internet-apps (mail, web, anything) can connect. They all just time out. I've switched airplane mode on and off, 3G and cellular data on and off, shutdown/restarted several times, and still I have no data. Has anyone else had this problem since upgrading? I will restore from my last backup if necessary, but obviously not having a data connection seems to be a big problem if it's iOS4 related.