Undo closed tab feature not working in Firefox 24.0

Hi friends,
I need a help here, I use firefox a lot for my all webbrowsing but I don't know what happened to it, "Undo close tab" feature is not working. I use "CTRL + SHIFT + T" and its not working from it. I also tested my keyboard , all keys involved are fine. I then tried to use right click tab --> Unto close tab but also it is not working.

I have Tab mix plus installed and feature is ON there but still not working. It is not very important feature but because I use it regularly, I am missing it a lot. I don't want to reinstall things, suggest solution where I can fix it without reinstalling anything.

I gave quick search over google for you and one of the solution was that if you have tabmix plus installed then disable undo close option and apply and then re-enable that option and apply (under tab mix plus menu). It should fix your problem.

ahan...thanks :)
for sharing.....................................