This turned out to be the solution for me.
For me, the Dock app was looking for a DefaultDesktop.jpg file and coulnd't find it. Chewed up to 75% CPU trying to locate it.
Thanks for your handy tip, I was able to see what the Doc was looking for.
To fix, for me, was to go into the System Preferences, launch the Desktop preferences and simply pick an image (any image) for the Desktop.
Then, went into the Monitor application and did a Quit on the Dock app.
Doc restarted and is back down to using ZERO % CPU.
All fixed now.
BTW : This particular system doesn't have Parallels or Fusion installed - so I knew those weren't the issue. Issuing the opensnoop command really helped!