I installed my first Avast version 4.6 and immediately was amazed by its feature. This is because it detects any virus in my removable drive right after I insert it in USB port.
But in 4.7, it didn’t detect it…regardless, I need to scan it… I really dissapointed…
avast! does not scan removable drives when they are attached - and never did.
It may be possible that some other program is “touching” the files… some old versions of avast! were not able to distinguish between “reading” and “starting” of executable files on some operating systems, so they scanned the files even though it wasn’t necessary.
It might be your case - hard to say without knowing the filename, at least.
Anyway, you can configure Standard Shield provider to scan selected files “on open”, if you wish.
Did you make a clean install? I mean, uninstall the version 4.7, boot, install the 4.6?
Like Igor said, avast did not scan removable drivers when attached…