Tim,
I have not seen this behavior on my OE with AVAST.
I will run some tests on my own system to see if the indications you describe can be duplicated.
At this point, I can only guess that Avast is detecting the "test virus" as it should, however, because you are sending it as an "attachment", you may need to run Avast in the normal scanning mode before the "functions" are actively working.
THIS behavior of Avast I HAVE seen on my own system.
Try a full scan and see if Avast picks it up in whatever folder you have it stored, then try to move it to the chest.
If you are succesful, then I would say that things are fine.
The main thing it that AVAST is on the job doing with it is supposed to do.....PROTECT YOUR COMPUTER.
I will get back to you as soon as I can run the tests.
Maybe a Moderator can help with some thoughts.