Have you filled out the Schedule NR, where you show the percentage of income sourced to Maine?  Like some other states, Maine tells you to figure the tax on all of your income, regardless of source; then figure the percentage of your income that is taxed by Maine; then multiply the total tax by that percentage. 

Taxpayers whose total income will put them in a higher state tax bracket, will pay more tax on the same amount of Maine income, as taxpayers in a lower bracket.

What entry do you have on Line 21 of Form 1040ME ?