What's That Noise? Unfortunately it's confirmation of your worst fears...drive-line failure on your bike.
This month is the Best of Forum series is a thread on drive-line failure, specifically U-Joint failure. This thread started some years ago and was recently picked up by one of the members. As the real nice riding weather fades for a lot of us and maintenance on the bike comes to mind, this thread has a lot of info on causes and repair possibilities. Remember the thread is "open" so you can join in the discussion.
Enjoy...and watch your fingers. Gary