These forums have lots of examples of popular antivirus/security packages interfering with things they shouldn't have been, including backups and Rescue Media creation. I just recently helped someone who turned out to have an anti-malware solution that prevented shadow copies from being deleted, which filled up their storage allocation to the point that Reflect could no longer create new shadow copies in order to perform backups. This type of nonsense is probably what led Macrium to create this KB article
-- although there are many other instances of third-party AV interfering with legitimate activity performed by other applications. For example, Norton/Symantec has been in the news twice recently for causing Chrome crashes when Google tried to enable a security feature in Chrome. Google reverted the update the first time to give Symantec time to get their house in order, and then tried again later with the same result. Before that, after Microsoft switched over to using a more secure digital signature algorithm to verify the authenticity of Windows updates, Norton/Symantec products started blocking Windows Updates from installing at all, a process they never should have been involved with at all given that Microsoft has its own authenticity checks built into that process anyway.
And of course the offending products practically never give any clear indication that they took any action that caused these negative outcomes, leading their users to ignore those products as possible causes of the behavior and instead blame the application that isn't performing as expected.
I dumped third-party AV pretty much when Microsoft Security Essentials arrived, and since moving to Windows 8 I've dumped it altogether. Windows Defender holds up quite well compared to the competition in independent tests nowadays, it's free forever, and every Windows developer designs with it in mind because it's there by default. Meanwhile, third-party AV seems to cause more harm than good these days, especially now that major Windows releases are arriving every 6 months, because the fact that they need to hook into Windows in ways that Microsoft does not recommend or support means that when Microsoft changes something that they shouldn't have been using, those hooks can bring the whole system down. Of course users tend to blame a bad Windows update when that happens because, "My PC worked before the update and now it blue screens during boot!", but it then comes out that AV was the true culprit. And then there are the times when AV creates
security vulnerabilities. Turns out that when you insert yourself practically everywhere in the system, a bug in your code can be exploited from practically anywhere. I remember a case again involving Norton/Symantec where its network scanning code had a flaw that meant a remote attacker could take over a victim's PC by simply sending it a few specially crafted network packets.
And some AV solutions expect you to PAY for this privilege!?