Our daughter was a full time student for more than 5 months, she lived with us and we provided more than half of her support for over 6 months. She had income of $8400 in 2010. She married in 2010 and is filing married filing jointly. My question is can we still claim her as a dependent?

She must be under 24. Also you can’t claim a married person as dependent if he or she files a joint return except that the joint return is only a claim for refund and no tax liability would exist for either spouse on separate returns. Your U.S. Tax Return: Requirements for claiming a dependent

She is under 24. But I am unclear on exactly what "refund and no tax liability" means. They are getting money back on their return because they over paid but they did make enough money that they owed taxes... they just had too much taken. Thanks for clarifying.