A within the last week my unstable mutt stopped doing a cool thing. After invoking mutt I used to type 'c' to change to a different mailbox, and then I would type '?' to see a list of all mailboxes in my ~/Mail directory.
Now, 'c' still prompts me to enter '?' to see a list, but typing '?' does nothing. After typing 'c' I can enter the full path to a mailbox, but I miss my cute mailbox list.