Pesky Authentication Issue
If you receive an error page that includes a URL with /2k//2k/ in it, please quit your browser and login to Lessons anew.
The 2k//2k in the URL signifies that you've tripped over a recently developed problem within the UM authentication environment. It's as if another authenticated UM service has been given the same "key" as Lessons, and by the time you visit Lessons the key is already checked out.
Unfortunately, it may happen to you again since it's your browsing pattern that's tripping the error and since most of us use the same authenticated UM sites and services on a regular basis.
We're working to track down the conflict, but since it resides outside Lessons, and since closing the browser deletes all meaningful evidence of the problem, it's been elusive. Our apologies.