This page is a show case for a problem I have since the build of Firefox 3.6.4 (which runs plugins in a separate thread). When you click in the applet it will call the JavaScript function 'alert' (or 'confirm' when Shift is held). This locks up my browser (prevents any interaction, though links opened from other programs will open in the browser).
One either has to kill the plugin-container.exe, or Firefox itself.
This does not happen in a 3.6.3 build.
Remarks:
Tested (and locks up) with:
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-GB; rv:1.9.2.4) Gecko/20100413 Firefox/3.6.4
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.3a5pre) Gecko/20100421 Minefield/3.7a5pre
In a few of many tries I was able to close the popup just fine, using the spacebar, or Escape. But a second click locked up the browser as before.
When pressing the spacebar (which would normally press the 'OK' button) and then killing the plugin-container, the popup closes immediately. This doesn't happen with a mouse click.