It used to be that hitting the refresh arrow/loop button in preferences -> account would pull down a new provisioning profile with all ur new devices.
Now it just downloads the ones you already have. But if the one you need updated is managed by Xcode, theres's no way I can find to add a device to it!
After adding the UDID in the member center I had the same issue. I have to say that I have a XCode managed iOS team development profile.
eventually what's worked is deleting the provisioning profile from the member center.
in xcode preferences, delete the team provisioning profile for the relevant app
go to your target, you'll see a "Fix Issue" button. click it, it will generate a new provisioning profile with the relevant devices.
Hope it helps.