Unresponsive Script window pops up all the time now. Why? and what to do?

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http://askubuntu.com – I don't know that it's for the exact same script each time, it may be. "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete." "Script: chrome://messenger/content/folderPane.js:721" This is in association with Thunderbird I think. This doesn't just happen after I've stepped away for a long time. It happens every time I click on anything. Things keep running that I'm clicking on. Just before this started as a constant problem, I was looking at addons etc, and something in Thunderbird de (HowTos)