The error refers to google maps object. Are you using google maps on the page you are trying to open theme-it from? 
No there are no Google Maps on the page. I tested it on the index page of 3 of my websites. None have Google Maps on them.
1. corporatecats.com.au
I get the JavaScript error message and then Dreamweaver stops responding.
2. primetimemeats.com.au
I don't get the JavaScript error but Dreamweaver stops responding. It seems to be while trying to display the preview.
3. firthwebworks.com.au
Same as 2 above.
We will definitely look into this early next week to try to find a resolution. We can probably just remove the script from the page you are theming before creating the preview. Thank you for bringing this to our attention. 
My pleasure, it looks like it's going to be a great extension, when I finaly get it to run correctly, I struggle a little with colour selection so it will help me immensely.


