I'm quite sure avast! itself doesn't try connect to Microsoft site.
When ashSimpl.exe is started, it displays the introductory help. The help is in HTML Help format (.chm). Maybe the Microsoft HTML help component is connecting to its site at that moment (for whatever reason... check for updates, improve searching... don't know)?
You can check if you get the same warning when you simply open the help file, located in <avast4>\English\Help\CheckListSimple.chm