I know this isn't something you can directly address since it's a custom theme, but I wanted to ask what core WordPress PHP code or call does TEC rely on to display the individual event pages or the calendar and list views?
I just checked and the plugin works fine on TwentyEleven, but I don't get anything except for the pre-text I added in the Templates section on a custom theme. I'm just trying to figure out what I should check. Note the theme is a little older than the newer versions of WordPress, maybe a little older than TwentyTen.
We are working with a standardized custom theme put together by a university for use by its departments, so I need to work on updating the theme a little to work better with newer WordPress code.
Hope you can help.