Hey Barry,
Thanks for the response, ohh dev team!
There are no other active plug-ins, and the current theme is WordPress 20-10. Switching to 20-11 made no difference on the error. The Eventbrite API key is correct; even made sure there was no trailing space at the end of it. =(
If it helps the site is also running on Apache version 2.2.23, PHP version 5.2.17, and MySQL version 5.5.28-log.