how do you know its clean if every AV say infected ?
what malware name is given on the file ?
is it detected as PUP ?
upload suspicious file(s) to
www.virustotal.com and test with 43 malware scanners
when you have the result, copy the URL in the address bar and post it here for us to see
Have you tried right click avast tray icon and disable shields ?
(dont complain if you get infected)