Hi Chris,
Sorry for the issues you are having. I can help troubleshoot this, but I might not be able to fix the coding if it is in the theme.
It sounds like a php fatal error is causing this when all three are active.
Can you please follow the section of the WordPress Codex Debug titled “Example wp-config.php for Debugging” on this page:
http://codex.wordpress.org/Debugging_in_WordPress
Please add that coding to your wp-config.php file.
Then try to active the theme and check the debug.log file after that to see what is placed in there.
Let me know what you find out.
Thanks