Thanks Mark -
I had the same thing happen to me, but can't duplicate it regularly. I'm able to get out of the loop by:
1. Signing into the April version, and signing out.
2. Switching to the May version.
3. Trying the link from Gmail again.
There are so many variables at play, and it's all related to shuffling versions of Method cookies, and betas of the Gmail talking to the live version of Method, while there is also a staging version of Method available.....I'm confident once the May version of Method goes live, this will resolve itself.