I have updated to version 5 from 4.8
In 4.8 I used Ash Quick 4 exe for virus checking on completion of the downloads with no problems.
In version Ash Quick 5 exe does not work,is there a different setting in Version 5.
Welcome to the forums, lankyknave 
You can use the right-click menu to do the same. Right click the file after the download completes. To do this, make sure the settings in avast are as below …
Open the GUI of avast > click on the Settings near the top left of the GUI > be sure the Basic tab on the left is selected > tick the checkbox under the heading of “Special Scans.”
Thank You CharleyO for your reply I did know about the right click menu option & I am set up accordingly but it was convenient to have it done automatically as with version 4.8.
The call to ashQuick.exe doesn’t work for me in Orbit downloader where it did in 4.8 and it doesn’t matter if that UI option is checked. Whilst I have also had an update to Orbit downloader, I rather suspect that it is ashQuick.exe under 5.0 that isn’t working as there are other reports of the same problem with other different downloaders.
I’m having the same issues with Gigaget and it didn’t have an update.