Such was the case with a recent update pushed out by the the folks at McAfee, the anti-virus software company.
Many companies and people on Thursday [April 21] were fixing thousands of Windows PCs that went haywire as a result of a seriously flawed software update sent by antivirus vendor McAfee.
The update distributed at 3 a.m. Eastern time Wednesday misclassified a critical Windows XP system file, called svchost.exe, as a malicious program. As a result, McAfee's AV software was instructed to detect and remove the threat, sending affected PCs into fits of rebooting that made the machines useless.
Fortunately my recently resurrected main computer was still off-line when the accidentally malicious software update was released, so it did not suffer the fate of so many other XP machines. (A note: my main computer also runs Linux, thank goodness). None of the other machines here at The Manse use McAfee (Deb's computer uses AVG and the other computers, which run Linux, use ClamAV).