If you’re developing on your shiny new iPhone 5s or iPad Air with Xcode 5.0.1, you may have encounter strange "screens of death" on your device.
These issues have been reported multiple times on Apple Developer forum  and there is a solution: Xcode 5.0.2 GM.
From the release notes:
Issues Resolved in Xcode 5.0.2 GM seed
Launching a 64-bit application on a device from Xcode multiple times causes the device to stop responding (and require a soft-reset). This has been resolved. (15338361)
If you’re developing with Xcode 5.0.1, trash it and go download Xcode 5.0.2 GM right now!