Above image from Red State
The image may look a bit akward; the very top part [the yeas and the nays] was spliced to the rest of the image due to space constraint. But go to the PDF file and examine the roll call closely, and you'll see that Nelson changed his vote. Also, there are two Senator Nelsons, hence, Bob Nelson's home state is listed next to his name. Bill Nelson from Florida voted 'yea' - and only voted once - heh.
From Red State:
The Senate of the United States just voted to table Jim DeMint’s proposed amendment that would prevent cash for cloture compromises.
As you will recall, Ben Nelson was bribed by Harry Reid to vote for the health care bill via targeted earmarks that will only benefit Nebraska.
DeMint asked for the Senate to suspend its rules to consider his amendment, which would prohibit such deals in the future.
Ben Nelson voted against Jim DeMint’s amendment, but when he realized the Democrats already had the votes to kill it, he raced back up to the clerk and changed his vote so the final record shows Nelson sided with DeMint.
Unfortunately for Ben Nelson, I have obtained the actual factual roll call sheet.
You can see it in PDF here.
Go to page two and find Nelson’s name. See the swiggly line through the mark on the left side? That’s the clerk noting that he switched his vote once the other Democrats defeated DeMint’s amendment.