I'm impressed: it works perfectly !
A small detail, though: for three of the files eicar.com and the ZIP files, avast! now triggers an alarm just after clicking on the file, as you said.
But in the case of eicar.com.txt, when I click, the content of the file is displayed in my browser. Now if I save it to disk, avast! detects the "virus" string.
I have no idea if this is a potential weakness that viruses could take advantage of, and again, I'm already very impressed by avast!, but I wanted to mention this for completeness...
Thanks for quick help !