This error is returned when your storage is locked for the android system and deployed APK can't unpack. This usually happens when device has SD card and it is mounted as USB storage to the PC. Since you state that the problem surfaced when the phone was disconnected from the computer, can you verify that your SD card is accessible at this time? You can check that by using a File Manager program and try to save/copy a file on it (e.g. image).
On a side note, you can try to build your application in "Release" and check if it works on your device. Use Graphite, right click on your solution in "Project Naviagor", select "Build Settings" and select "Release". Delete the app from the phone before trying to deploy again. This would verify whether the problem is SD Card/ Internal Memory related.
All the best,
the Telerik team
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