"Extension will not be installed because it does not provide secure updates" Warning in Firefox 3

How annoying. I just want to install an extension for ImageShack and it won't let me.

A way to get around this is to disable another new security feature by typing in "about:config" into the address bar and add a new boolean key value called "extensions.checkUpdateSecurity".

Set the value to false and try to install the extension again.
Should work like a charm.