Yours seems to be just the latest in an increasing string of posts indicating that, since the last update, VirusScan has, under certain circumstances, become virtually unusable. My major problem is with large avi files (varying from nearly 20GB up to a max of 60GB) - reported in another post, which are taking several hours to scan, per file (but didn't before the latest update). Others have reported slow scanning with different file types. In my case, I'm using whitelisting of the problem files as a temporary work-around but that simply means that now a full scan is not really a full scan. Even so, the remaining, abridged scan lasts more than twice as long as as a full scan used to do.
Perhaps by now, the people at McAfee might be getting the message that they've made some seriously problematic changes to their software and will be looking at what they can do to put it right. Otherwise there are likely to be a number of users looking around for an alternative security suite that they can use sensibly.
We discuss most causes. The 2011 version does stick on avis (large) so we exclude them after checking they are oK. The real time scanner will still scan them on opening.
The uninstall idea is worth a go. Haven't seen any issues on my PCs that have 2011 installed direct so might be a clash with another scanner (1 that scans in real time such as paid version of Malwarebytes) or a corrupted install.