"Cheatin’ uh?" Message when Selecting a Theme

Hello, I am having a problem with eNewsletter. I have created a custom theme based on your them "Minimise". The plugin installed fine, and I have able to select the various themes, but when I active a theme, the ajax icon runs then the "Cheatin’ uh?" message is displayed.

The is is NOT a Multisite. Just a single WP site?Versions:?WP: 3.5.1?E-Newsletter: 2.2.3

Any ideas on how to stop this error?
Thanks!

Here are some log entries I found using wp-debug:
[16-Jul-2013 23:02:35] PHP Notice: Undefined index: in /home/foo/public_html/domain.com/wp-content/plugins/e-newsletter/email-newsletter-files/class.functions.php on line 1767?[16-Jul-2013 23:02:35] PHP Notice: Trying to get property of non-object in /home/foo/public_html/domain.com/wp-content/plugins/e-newsletter/email-newsletter-files/class.functions.php on line 1767?[16-Jul-2013 23:02:36] PHP Notice: Undefined index: subject in /home/foo/public_html/domain.com/wp-content/plugins/e-newsletter/email-newsletter-files/builder/class.builder.php on line 788?[16-Jul-2013 23:02:36] PHP Notice: Undefined index: subject in /home/foo/public_html/domain.com/wp-content/plugins/e-newsletter/email-newsletter-files/builder/class.builder.php on line 788