I found that Avast writes to the registry after updating the program, Spywareterminator sees this writing and stops it.
Hi…
Does Spyware Terminator allow you to create exemptions for a particular program?
Best Regards…
As far as I can see no.
Hi…
Write to the software vendor of this particular program to get instructions on how to create exemptions. If they didn’t create this option in the program or they don’t respond, then the only think I can suggest is to see if deactivating the background scanner (while you update avast) works without any problems, particularly when turning it back on.
Someone else on this forum may have an easier, better suggestion than I do concerning this. 
Best Regards…
Thanks, I did mention this on their forum
I no longer use ST (didn’t like the interface or that fact that some of the options aren’t clear), so I can’t recall, but I believe there is a setting in the options, etc. about what it protects, registry, startups, etc. If you can find those you could temporarily disable the protection and then reinstall avast.
I would have to say I’m surprised that it didn’t give you the option to allow the changes when it first alerted you to them ?
If it didn’t that is most certainly a failing in the program IMHO.
Is there not a quarantine of some form (shows how much I have forgotten about ST) where you can reverse any decisions/deletions you have made ?