I downloaded the 32bit and 64bit portable versions (zip files) and the web shield never alerted. I have done an explorer scan on them in my downloads folder and no alerts.
They checked out clean here too, but running the HDCleaner executable produced the alert.
Edit: grammar
It isn't actually a full blown alert as such, but blocked and there is an option to set an exclusion. For me that is the Hardened Mode, which I have enabled and set to Aggressive, this checks files against the avast database. If there is no record of that hash then it would get blocked, as far as I can recall, Hardened Mode - Aggressive isn't a default setting.
So this is usually related to a file that avast is coming across for the first time, is this the Alert you are talking about ?
EDIT: Adding an exclusion allows the program to run, it would still be scanned by the file system shield.