I know this is long time ago, but since I had the same problem from the same kind of command (xcopy targeting a volume root with /x), I thought about sharing the solution. 

This appears to be a bug in xcopy (Windows XP SP3 version 5.1.2600.5512 at least), where the root directory entry ”.” of the target directory gets its ACL erased.

Fixed it with ”CACLS [drive letter:] /g Everyone:F”.

Getting access denied on the destination drive partition. after using xcopy
Is there a way to use a standard Matrix Keypad to set a synchronous counter IC without having to use a micro controller?
