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In Lr 4 that file looks perfectly fine with process 2012 and also with 2010. The only way I can generate the effect is to apply some defringe CA. In general, when you do that to an edge that has some purple fringe in it then Lr will fix all edges with purple and can therefore cause problems in other parts of the image.
In the 2010 process I even tried using recovery to cut the highlights back. Sometimes that can cause grey borders if overdone (which is really quite easy). The 2012 process does not have "recovery" but the highlight slider does a similar thing with far less chance of causing the grey borders.
Is it possible that you have synchronised settings from one photo to others and inadvertently taken some defringing with it ? Even if it was, resetting everything in this image should have fixed it unless you didn't reset quite everything.
It definitely is not something in-camera or I would not be seeing the healthy image.