new PopUp Plugin crashing my site

Hi,

I just installed the new PopUp plugin but the following happened:

1. I installed and activated it and then went to settings
2. In addition to the default settings, I selected to show Category options and one other setting and submitted the changes
3. Soon as I did that, my admin panel went white, totally no content on the screen. Same for the front end.
4. I deleted the plugin via FTP and the site went back up and running fine
5. I re-installed the plugin and it crashed the site again

Please let me know how to fix this. I am hosting on WPEngine.com and I have created Support Access for you.

Thank you very much,

David