The more you check, the more errors you find.

Freedom to Tinker has a good post by Ed Felten on a discovery by the Humboldt County Election Transparency Project, as reported in Wired.

Election officials in a small county in California discovered by chance last week that the tabulation software they used to tally votes in this year's general election dropped 197 paper ballots from the totals at one precinct. The system's audit log also appears to have deleted any sign that the ballots had ever been recorded.

Yes, the vendor was Premier Election Solutions (formerly known as Diebold), and yes, it was (at least) a software bug that persisted over numerous versions of their system.

Apparently, Diebold/Premier optical scan systems aren't that much more trustworthy than their direct recording electronic (DRE) voting machines.

At least they had paper ballots to check against. Making them available on the Web is a brilliant policy stroke.