BitDefender antivirus update quarantined hundreds, sometimes thousands, of legitimate files on Windows 64-bit systems. Some customers stranded by the update have demanded refunds and compensation for money spent fixing their PCs. The antivirus company acknowledged the problem and released a patched update and workaround instructions Sunday. The number of affected users is “very small, a few hundred worldwide,” Bitdefender’s global marketing director says. “Each case is different and unique, and we’re addressing each individually,” he says.”]