McCain way overspun it, but it is true that Obama voted to raise taxes on single taxpayers making 42k.
http://uselectionatlas.org/FORUM/index.php?action=printpage;topic=80556.0
A TV spot claims Obama once voted for a tax increase “on people making just $42,000 a year.” That’s true for a single taxpayer, who would have seen a tax increase of $15 for the year – if the measure had been enacted. But the ad shows a woman with two children, and as a single mother, she would not have been affected unless she made more than $62,150. The increase that Obama once supported as part of a Democratic budget bill is not part of his current tax plan anyway.