Workaround info 1 [edit](I prefer the first paragraph of this one over the second para/link below.)
Workaround info 2
Info and download for a test virus.
Other AV links:
I'm quite a fan of Avast. If I couldn't use it I would be almost as happy using
Avira or trying out
Microsoft Security Essentials. (Both homepage download links.)
Why Avast over the others?
Thing is with a lot of the freebies, some aspect of the free version is crippled in some way, so as to distinguish it from the pro version, else none of these companies would make any dosh, Tosh.
Most of them part-cripple the detection, cleaning, updating etc. Which makes them less effective when the bomb drops. Avast cripples the ability to schedule a scan. (And cripples what's called "push" updates, where critical updates for new detections are released to the pro clients as soon as they've been analysed and nerdified so the program will accept them. Gives a slight head start.)
Comparisons:
Probably the definitive site for AV performance comparisons, is
Av-comparatives. AFAIK there is no other site carrying out truly independent and comprehensive/relevant testing. (And nothing reputable for free AV's.) Avast always scores quite well or excellent. SO do Avira and (usually) AVG. Pertinent to remember, though, that only the pro AV's are tested. So the rankings, as regards the free versions of AVG and Avira, mean little for the users of those products. Whereas Avast has the same detection/cleaning ability in the Home or the Pro version. (A signification reason many users are very happy with it.)
Why files found on scan but not in realtime?
Without seeing the file names and paths, this is pretty much impossible to know. A likely scenario is that they are leftovers of something, (or actual full malware files) that Avast did not detect when they first appeared on the PC, for which definitions were later added. That the resident shield has not alerted to them before now suggests they are dormant/never run/never activated.
Or they (or some of them) are false positives. The word "gen" as part of the detection name indicates an increased possibility of this, if present.
Try uploading the files flagged as malware to
VirusTotal - Free Online Virus and Malware Scan for an online scan. Once the scan has completed, post back the URL to each results page. (not the permalink info, the actual URL.) Files can also be sent to Avast from inside the chest (quarantine). If they are suspect FP's, Alwil are pretty on to it about removing the detections. The files should periodically be re-scanned in the chest, to check status. Don't delete them. At least, not yet.