As much as I hate Franken, and believe me I do - the tax thing is totally blown out of proportions.
There was a law enacted saying that if you perform your job within a state you have to pay those taxes in the state, even if thats not your home residence. So Franken traveled around the country doing comedy shows, but only paid taxes to his home state.
It isn't like he didn't pay the taxes, its that he paid the taxes to the wrong state.