
What fixed it for me was to go to the Immunize panel, make sure the only items checked were the ones relating to Mozilla/Firefox, then click Undo.
This could be different in your case if you get this unresponsive script warning, but the ultimate fix to this I recommend is updating to latest version of Firefox which fixes these warnings and bugs. It looked hung and unresponsive but just needed a LOT more time to finish loading, then worked normally (well, except for the slowness). With the current trend of web services springing up, there is no shortage of remote services driven by Javascript which you may want to add to your site via