I would definitely contact Apple on this, if you have a local Apple store make an appt and stop in to see them. It could be a carrier related issue or something in the device itself but the hard part in trouble shooting random things is well their random. I had that issue with a phone and the Verizon person I had to deal with was, well a challenge to put it nicely. That is one thing I do prefer about iOS devices is I don't have to deal with the carrier tech support that knows far, far less than I do about the devices I use. The forums are typically a great place to post and get advice about. I would also post this over on a few other forums you may already be visiting like Macrumors.com to see if anyone else has been having this issue. Sometimes you need a larger base of users to get advice from.