In case anyone is interested, here's a test tool that you can be used to test the avast! autosandbox feature.
It's a tiny program that creates a file in the root of disk C:\ and in the registry Run key.
Avast should trigger the autosandbox feature on this file, so you can test whether the feature is working as expected (in the latest version 6.0.1091, it should work on all supported OSes). If the file is not autosandboxed, there may be some problem.