Rated 5 out of 5 stars
works perfectly on ffox4.1
type: about:config in ffox
then: browser.sessionstore.max_concurrent_tabs *set it to 0 *
then install unofficial bartab (found it here in comments)-> http://www.filedropper.com/release. official works too, but tabs needs to be reloaded. and you need install "Add-on Compatibility Reporter" to be able install it.