Hi,
try the KasperskyScan on the file(s)
..\Avast4\Data\chest\
if they're encrpyted by AVAST too well, even kaspersky won't find anything there, however .
In that case:
-remove all and any startup-Calls to the file in the registry-RUN-keys, win.ini, system. ini etc..
-make sure to close all unecessary/malign processes
-extract (NOT restore!!) the file from the chest; move it to new empty folder outside of the Windows(programs-folders..
-scan it with kaspersy there..
note the exact name and get back here, or search in virus-Databases/google