Yesterday I used WordPress's auto-upgrade function to update my copy of the BTEV plugin from 1.8.1 to 1.8.2. When I went to log into my blog today, I received a SQL error saying
custom_source was missing from
wp_btev_events (forgot to copy the exact error). I checked the table in phpMyAdmin and dug through the plugin code. I found 2 new fields in the plugin which were not in the table on my site. Running the following ALTER statements fixed the table and let me login. Not sure why the plugin did not automatically add them, but figured I'd post about it to help anybody else with the same problem.
ALTER TABLE wp_btev_events ADD COLUMN server_id int(11);
ALTER TABLE wp_btev_events ADD COLUMN custom_source varchar(255);