I know this question has been asked quite a bit before, but none of the known causes seem to be the case in my situation.
The device is provisioned & connected. I can see it in iTunes as well as the XCode organizer and it's marked 'green'.
It is also set up for development and has the provisioning profile used for development installed. The profile is also present and valid in the XCode organizer.
The project & target 'iOS Deployment Target' is definitely below that of the device (deployment target iOS 3.0, device is 6.0).
The device is added to the development provisioning profile in the apple dev site.
Any idea what else could be causing this problem? I should add that my XCode version is 4.6.3.
Answering my own question here. Wasted a bunch of time on this, but sometimes it's the simplest thing that kills you. It turns out someone on my team had changed the target's supported Device (under Targets -> APP_TARGET -> Summary -> Devices in the project settings) to 'iPad', when the app was supposed to be 'Universal' all along, and I was trying to deploy to an iPhone.