zClip freezes Firefox up

Used this plugin for a long time, but recently it started badly freezing up my Firefox. Works fine in Chrome and even IE (!).

Is it a Firefox bug associated with some sort of incompatibility with Flash? I am using the most recent versions of Firefox and Flash Player as of this moment:

Firefox: 18.0.2
Flash Player: 11.5.502.149

To test, just click the "Copy" button on their website: http://www.steamdev.com/zclip/

To unfreeze - right button click the browser tab (also weird).

enter image description here

Solution

This is a regression in Firefox 18 which should be fixed in Firefox 20. It shouldn't happen with newer ZeroClipboard versions though (see comment 12), so upgrading it might be a work-around.