I found what causes the appending of the "_VW12", "_VW12_VW12", "_VW12_VW12_VW12"? etc.
Open a VW file created in a previous version of VW in VW2008, you will get the dialog "This file was created with an older version...." at the bottom of the dialog is a Settings button. Select the Settings button, you will get another dialog "Keep the original file name with the:" and you can select from "Original File" or "New File" if you choose "New File" and then attempt to Batch Convert you will get the appending "_VW12", "_VW12_VW12", "_VW12_VW12_VW12"? etc. So as a work around for now, only choose "Original File".