The problem's gone when I run Word in safe mode!!

However I've run both Quick and Online repair, but the problem is still there. I've also disabled the only add-in I had enabled and I also removed GM's template add-in from the Start up folder, but none of it is solving the problem when running Word normally.

When I create a new document, it shows up correctly in Letter mode. But when I open an existing document, it shows up in Email Message format and I must manually change it into Letter