Hi DavidR,
Many thanks for the reply... we've got the same boot scan failure issue on Avast installs on three different OSs: XP (SP2), Win7 and Win10 (Pro, 32-bit).
The Win10 install - which we're most concerned about, as we're still new to the OS - is version 12.3.2280 (build 12.3.3154.2).
For Win10, I did indeed check in Program Data\AVAST Software etc. (Folder (view) Options for hidden files/folders and protected system files are set to visible). There's definitely no ASWBoot.log.
I have submitted a ticket, but sadly it's now been over 2 days without a reply.
Without confirmation that this is a glitch with the Avast app., we don't know if it's something nasty (rootkit etc) interfering with the boot scans. It's not the glitch that's annoying; so much as the waste of time trying (scanning, isolating PCs etc.) to work out what might be at fault (e.g do we have a virus etc.?)
(Although, we have run several BitDefender 'Rescue Disk' scans, it's free to download and boots direct to a Linux-based gui from a CD, and nothing has been found so far).
Anyway, thanks very much for he help and kind regards!
P.S. We've also checked the HD for the Win10 install (using the HD manufacturer's proprietary low-level disk scanning software) and no faults/errors have been found....