An major electronic voting system vendor has changed its story in an attempt to explain how its machines dropped hundreds of votes in Ohio's March primary elections, saying it was a programming error, not the fault of antivirus software.

E-voting machines from Premier Election Solutions, formerly called Diebold Election Systems, dropped hundreds of votes in 11 Ohio counties during the primary election, as the machine's memory cards uploaded to vote-counting servers. Premier originally blamed conflicts caused by antivirus software from McAfee, but the company this week said a logic error in the machines' GEMS source code was responsible for the problem.

"We now have reason to believe that the logic error in the GEMS code can cause this event when no such antivirus program is installed on the server," Premier President Dave Byrd wrote in a Tuesday letter to Ohio Secretary of State Jennifer Brunner. "We are indeed distressed that our previous analysis of this issue was in error."

Numerous tests by voting authorities had failed to identity the logic error before Ohio discovered the dropped votes, Byrd wrote.

The antivirus software could trigger the error, but it wasn't the underlying problem, said Premier spokesman Chris Riggall. Premier's earlier analysis "was not complete," he said.

Premier also released a product advisory notice on Tuesday, telling users of its e-voting machines running some versions of the GEMS software how to avoid lost votes. Poll workers need to check the vote-counting servers to see if all memory cards are shown as uploaded, the company said in the advisory.

Premier has also developed a fix for the logic error and is now testing it, Riggall said. The company has submitted a version of the GEMS software for federal certification, and Premier will submit the bug fix as part of that process. But the fixed version of the software won't be certified by federal elections officials before November's election, he said.

Tests by Brunner's office and Butler County voting officials had dismissed Premier's earlier claim that antivirus software was the cause of the problem. Officials in Brunner's office discovered the dropped votes in other counties after voting officials in Butler County found about 150 dropped votes. The votes were eventually counted in the March primaries, according to Brunner's office.

The IDG News Service is a Network World affiliate.