From what I've learned so far, the state in which you are considered "domiciled" is the state in which you pay taxes, even if you aren't resident there. Now, this could vary from state to state, but MN would tax us on our UK income if they considered us domiciled in MN. I guess how they decide the state you are domiciled in is the state in which you would be living if you lived in the US.
Anyway, we took care of that problem by putting our stuff in storage in WA (at DH's parent's home) and we also own a vehicle in WA. Thus, if MN decided to come after us for taxes after 2002, we can successfully argue that we are domiciled in WA, which has no income tax (a nice bonus!)
As I stated before, regulations vary from state to state, so check your states regs. The IRS links on the American Embassy website give links to state tax depts.
Our former home state (MN) taxes almost everything, and heavily too, so we have been proactive to avoid any tax situations from MN after 2002. I'm 99% sure that we won't live there again, so no worries there.
JR, thanks for the clarification about the extension and still having to pay interest. We will be getting a refund, so that shouldn't affect us, but it's good to know anyway. As far as tax rate, they've been taxing us at the highest rate for the past 5 years, so they can't tax us any higher!!
Stephanie