Latest TMP Dev build 0.4.0.4pre.120724 seems OK, indeed Rated 5 out of 5 stars
tab_mix_plus-0.4.0.4pre.120724a.xpi at https://bitbucket.org/onemen/tabmixplus/downloads (latest working version) seems to works fine here as well as others have mentioned. There is in TMP forums another "non official DEV build update" (that is, an update to the official latest DEV 0.4.0.4pre.120724a) labeled 0.4.0.4pre.120724b which here does not work at all. Sticking on the developer's latest Dev build seems to be the right choice at this time.
Just one word to Firefox users (hi, there!) who declare that they'd be about to leave Firefox for another browser on the basis of one add-on not working right on latest Firefox : I am stunned to read that. It's like quitting a girl-friend because of her new haircut :) Gosh, if you like her, and/or Firefox, keep it goin', man :)