Way to go!

For those with Firefox 3.5.x or higher, FYI, you can use that ccleaner program or, to do it manually in 2 steps-

In Firefox, go to Tools, Options, Privacy button at top. Click on Show Cookies button in the bottom right. Click on Remove All button.

Secondly, go to Tools, Options, Advance button. Click on the Network tab. Click on the Clear Now button to delete the offline cache file.

Close the browser and re-open. You should be good.