On http://www.speedrunslive.com, stream viewers can normally chat in a little box that's linked to the streamer's Twitch chat after clicking a small pop-up that states what that streamers' chat rules are, and that you agree not to break those rules. With PB installed, the popup keeps appearing infinitely. To illustrate this:

Without PB:
Click on the chat field.
Click "OK" in the pop-up that appears to agree to that streamer's chat rules; the pop-up will disappear.
You can now type in the chat field.

With PB installed:
Click on the chat field.
Click "OK" in the pop-up that appears to agree to that streamer's chat rules; the pop-up will disappear.
Attempting to type or clicking on the chat field makes the pop-up appear again.
Click to confirm; it disappears.
Attempting to type or clicking on the chat field makes the pop-up appear again...