I'll have to debug this with you directly. It appears to be working for me. Maybe try reinstalling eCart... it is possible that if you have an older version of another extension installed it might have overwritten the themeit UI.
If that still doesn't work, post back with a US phone number or skype contact information and I'll set up a screen sharing session to debug this with you. The issue is that it isn't creating the preview file properly. That would prevent it from both displaying and click to preview as well as the interface not working in general.