i did try to contact Apple on the same issue, but after 2 weeks of emailing and a phone call I didn't get any explanation for this issue, I also don't understand why... i did find some article from apple docs that say that this can happen if this device was installed with another developer account that violates Apple guidelines. but i don't know what account, as a developer we build a lot of apps and Xcode asks for a device... (we can't buy a device for each client ...) i don't really understand why Apple makes it so hard for its developers