Recently i updated echofon addon for firefox and it stopped working on my FF 3.6.8 showing an error message. I was unable to use echofon. So today i found a solution and it is working again. Actually it is not solution for recent updated version.
To solve this problem i installed the old version of echofon again and it is working fine now.
Here is the link ==> https://addons.mozilla.org/en-US/firefox/addon/5081/eula/88620?src=version-history
Hope it helps those having similar problem.