well, the 6D is in an authorized canon service center...
the guy at the counter looked at it and quickly diagnosed it:
"its gonna be the shutter... it sure is the shutter... unless its something else"
I'm glad that its still under warranty and hope they have a good technician (and a 6D shutter in stock)
Unfortunately, shutters can die prematurely, or last forever. They fail on a bell curve, so most of them last for X actuations.
If you bought it with a American Express card, they double the warranty, so you actually have a two year warranty. I make it a point to do that.