Got this error during setup of Windows Deployment Services on Windows 2008 R2. I used a standard boot.wim and install.wim file for the install. After doing som backtracking I found out that I had misconfigured a setting for the automatic naming of the machine name in the domain. I had used NN-%username-%# in the WDS properties, and that caused the machines to all trying to use the same name (NN-administrator-1).
After changing to NN-%username-%03# the problem was solved.