I'm sure there's a thread about this problem around here somewhere, but I haven't been able to locate it; however, I have found several mentions of it on apple's discussion site (which unfortunately I find quite difficult to search on). Here's an example: https://discussions.apple.com/thread/3437795?start=0&tstart=0 I've been experiencing this problem about once a day, sometimes more. My phone will show bars and the 3G symbol but simply will not connect. Switching to airplane mode and back doesn't seem to work either; the only solution is to turn the phone off and then back on. Of course, I then get a flood of notifications, missed emails, etc. It's not the only place that it happens, but I often notice this issue at a particular time of day and particular location (the afternoon, either during my gym workout or shortly thereafter). I have no idea why that might matter, though. It definitely happens at other times, as well. Anyone else experiencing this issue?