After a long history of incidents/accidents, I’ve been using my iPhone 3GS (new bootrom) with regular iOS4 for a couple of days. However, I had to do without any mobile internet – even though my contract was fine and it had been working just fine with 3.1.2.
I’ve pretty much tried every instruction that’s out there which has anything to do with enabling mobile internet. Removing SIM-card, resetting APN (even though my provider doesn’t even need any APN settings), completely resetting network settings – along with disabling+enabling mobile data connections and/+ 3G for a thousand times. The “E” or the “3G” was showing up fine (depending which one I enabled), nevertheless, no connection could be made from any app.