KCMW--you might get your gridlock yet, after a fashion; remember, Lieberman won in CT, which means that he now has more clout than ever.
Technically speaking, the Senate now stands at:
49 Democrats
49 Republicans
1 Independent Socialist(!) (Bernie Sanders)
1 "Connecticut for Lieberman" (Joe Lieberman)
...except that Sanders has always voted with the Dems (and actually won the Dem primary in VT, I believe).
As someone elsewhere pointed out, Lieberman no longer has any reason or need to "switch" to the GOP--he'll actually have more leveraging ability as a "technical" Dem than he would if he officially switched over.