I fixed the problem I think, somehow some browser toolbar loaded to my ff and I uninstall it. Than this pop-up gone.

I have the same problem. I first encountered the pop up 2/22/2012 while visiting coupons.com. I updated to Firefox 10.0.2 plus all add-ons. I am still searching for the source of the problem. If disable add-ons, and restart it does not occur.

I have just a few add-ons , which are the basics.

disable startnow toolbar

It is in Tools>Add Ons>Extensions

There is an extension called Start Now Toolbar.....just remove it.

After investigating, the pop up seems to be coming from www.dropinsavings.com.

To opt-out go to http://www.dropinsavings.com/optout.php.

Their site also gives you instruction to uninstall the add-on. Check out the picture I uploaded.

You have to kill it in two places. FF must be generating revenue from this.

Goto Add-ons

1) Click on the Plug Ins tab.

   Disable both "Coupon Inc" addons.  For some reason I had two.

2) Click on the Extensions tab

   Disable the "Start Now toolbar"

What a pain.