I'm not the first to post about this but I haven't seen you respond yet about this issue. I am using your widget for a client site, so I need a fix for this or I can't include the plugin on the deliverable site.
As others have stated: sometimes (can't figure out WHAT causes this to happen) when you open a WYSIWYG Widget, and click in the text area to launch the WYSIWYG editor, the WYSIWYG editor window is blank and no amount of waiting causes it to load. Just a blank area.
Wait a few minutes and try again and then it works fine. No rhyme or reason (I've tried to get it to break when working, and tried to get it working when broken - can't figure out what causes this to happen intermittently.)
I have seen you post that you're working on an update - soon - is this something that will be fixed? Your plugin appears to be the only one that provides this functionality, so I really don't want to uninstall it, but as I said I can't release a buggy plugin with my finished client site...
For what it's worth, when the plugin is working, it's really awesome. I hope that you do continue development.