Did you convert some or all of your traditional IRA to a Roth IRA in 2010? Generally the amount converted would be taxable in the year converted. But in 2010, you were given the opportunity to spread the additional income over 2011 and 2012.
Not sure if you did a conversion or what your tax preparer did? Then I suggest you dig out your 2010 tax return and take a look.
You might have to include part of that conversion as income in your 2011 return.
For more information on IRA conversions, see IRS Publication 590.