A Google Maps Help thread has several business owners complaining that they keep getting an error from the Google Local Business Center category field that says:

The issue is not that Google is now requiring businesses select a pre-defined category but that even when they do, they still get this error.

Mike Blumenthal has a picture of the error warning shown to these businesses.

There seem to be a small spike in complaints about this error in the past week or so.

Forum discussion at Google Maps Help.