Change close button image location

I am using a security plugin that changed my wp-content directory to simply “content.” My-calendar seems to work fine with this enabled, except the close button on the date popup window. It’s linked to /wp-content/plugins/my-calendar/images/event-close.png. Can you point me to where this directory is set, so I can re-write the location?

http://wordpress.org/extend/plugins/my-calendar/