Firstly, seriously consider giving up the whole "daily scan" thing......unless you really want to for peace of mind. But Avast! scans everything on-access already, part of the benefit of having an AV always running in the background is getting to do away with a daily scan routine.
As far as the results go....Avast! will always return this result on any pass-protected file. Because it knows not what the password is. Why is it returning this result now, but not before? 2 possible reasons come to mind......either an Avast! update led to scanning in an area that was not scanned before...or Secunia started pass-protecting files that were previously not.
Either way, the results are safe to ignore.