Brett/Victoria,
I plan to put in an auto check/fix, possibly in dailymail or on the login page, ASAP. This seems to be a very rare occurance (I get about 1 request every few months on this), but if you need it sooner, let me know.
You can run the command manually in PhpMyAdmin (once logged in) by clicking your ListMail database on the left hand side of the screen. Then, click the "SQL" button at the top of the page. Here you can enter your custom commands, such as the following which repairs the user table:
REPAIR TABLE lm_users;
Regards