I have just run a test using the eicar.com file (copying it from an excluded location into the open) and avast alerted and I sent it to the virus chest, attached images 1&2.
I then selected Restore from the virus chest, attached image 3 and that sent it back and cleared the virus chest, attached image 4. For obvious reasons I didn't send it for analysis, so I didn't test that function.
Have you tried an Avast Repair ?