Amending returns

I am attempting to amend a 2007 return, and following the instructions from the "help" function, I made my changes in the Federal return. The 1040-x shows the following changes:Line 1 AGI Line 2 Itemized Deductions $30Line 4 Exemptions 0Line 5 Taxable Income The problem: Even though taxable income decreased from $176,971 to $175,469, there was no reduction in tax liability (line 6) or total tax (line 10) I know the tax should have reduced, so what am I doing wrong? Thanks for the help.