I can’t tell for sure due to the sheer density of the text, but it looks like you’ve got a full form, including a fair amount of javascript in the body of the Exit Notifier. My only guess is that it’s something in the javascript creating a popup window that’s being blocked. Without extensive cleaning up of the code, I don’t really know what to tell you specifically.
First, please cut the entire body to another text editor or something else to save it, and just type some simple text and see if you still get the popup block. If not, then it’s something in the code you’re adding to the body of the Exit Notifier window. Let me know if that changes it for you.
On another note, my misunderstanding of your second point above led me to add another feature. I’ve credited you in the changelog. Now you can add custom attributes to a link and customize the title and body for every link if you choose.
Do let me know if you still get the popup blocker with plain text in the body.