EFS encrypted file, impossible to delete

I have a SBS 08. A user received some files send from a mac. He unzipped it with his windows 7 locally and copied it on a network shared drive on the SBS. The files (some fonts) were already in green color and encrypted just after the unzip.

So now I have those files on my server, and my little backup tool (SyncBackSE) stuck on them.

I tried to delete them, as domain admin, being owner with full access, nothing, I have to kill explorer.exe process.

We tried with the user that copied it on the server, still freezing explorer.exe !

I read about the LocalSystem user, and tried a couple of things to execute a cmd.exe with 'super power' but unsuccesfully.

• at … /interactive cmd.exe is
  deprecated
• create svc binpath="cmd /K start"
  type=own type=interactive doesn't
  work
• psexec -i -s cmd.exe I got this :
  Could not start PsExec service on
  BVMEDIASERVER: The service cannot be
  started, either because it is
  disabled or because it has n o
  enabled devices associated with it.

What else can I try ? Thank you !