Those software failures are likely to send Diebold programmers back to work and perhaps force the firm into weeks of independent laboratory testing.

With 17 California counties — including Alameda, Marin and San Joaquin — considering purchase of the Diebold AccuVote TSx, as well as dozens of counties in Ohio, Utah and Mississippi, the delay could put at risk tens of millions of dollars in sales and throw open the door to Diebold competitors.

In Alameda County, Diebold's first large customer on the West Coast, local officials are eyeing other manufacturers' products and mass-mailing county voters to promote the virtues of absentee voting — no need to come to the polling place and use an expensive voting machine.

"We're looking at all of our options," acting county Registrar of Voters Elaine Ginnold said. "That means looking at every single voting system" that California might approve for voters.

For years, the county was considered Diebold territory. Other vendors, such as Sequoia Voting Systems with Oakland headquarters less than five miles from county offices, figured a sales pitch was wasted time. But Keith Carson, president of the county supervisors, suspects those days "have to be more at an end than not." "As far as the other supervisors," he said, "I can't believe they would continue down this dark path with Diebold when there are more problems with each testing."

California Secretary of State Bruce McPherson ordered the mock election after paper jams plagued Diebold's TSx in earlier tests. The machine is mated to a printer so voters and elections officials could verify electronic votes.

Software problems occurred in those earlier tests, but state voting-systems analysts were more focused in the mock election on paper jams. Yet when Diebold representatives trucked in 96 brand-new TSx machines, and local elections officials voted on them July 20 in a San Joaquin County warehouse, nearly twice as many machines froze or crashed as had paper jams.

Last week, McPherson rejected use of the TSx, saying the machine's lack of reliability "isn't good enough for voters in California, and it isn't good enough for me."

On the strength of the paper jams alone, two-dozen critics of electronic voting rallied in front of the Alameda County administrative offices Tuesday and demanded county supervisors withdraw from negotiations to buy the machines. Homemade signs accused the McKinney, Texas-based maker of voting machines of "stealing" elections and called on Alameda County to "dump Diebold."

"There have been serious problems for years now, and it's time for the board to take responsibility," said Judy Bertelsen, a Berkeley leader in an umbrella group, the Voting Rights Task Force.

In all, 19 machines had 21 screen freezes or system crashes, producing a blue screen and messages about an "illegal operation" or a "fatal exception error." A Diebold technician had to restart the machine for voting to resume. Ten machines had a total of 11 printer jams. Almost a third of all machines in the mock election had one problem or another.

Diebold officials say they plan to fix the problems and bring the machines back for a new mass test in late August. But they have confided to some California election officials that they aren't certain what caused the touch screens to crash.

Douglas Jones, a computer science professor at the University of Iowa and an expert on computerized voting systems, isn't surprised.

Diebold's touch-screen machines run software written by Microsoft, Diebold and at least three other companies who make parts such as printers, memory cards and the touch-sensitive screen itself.

It's essential, Jones insists, that Diebold take its software and hardware fixes back through independent laboratory testing. Otherwise, the patch risks creating a new and unpredicted problem.

"Especially with this blue-screen problem, you don't know whether it's the printer drivers, you don't know whether it's Diebold's own code or whether it's Windows, or where the problem is," he said. "It brings into question the entire system."

Contact Ian Hoffman at ihoffman@angnewspapers.com.