It may be a corrupt normal.dotm.
Try deleting it.
Close Word, find where normal.dot resides (should be in the same folder as Author.dot) and delete normal.dotm
A new one will regenerate next time you open Word.
Another cause could be other product's dot files that are installed to the Word start up folder.
These may over-ride the Author.dot
Examples are the snagit.dot, palm.dot, etc.
Remove these from Word's startup folder and see if the behavior persisits.