Problem: Office Web Apps on a developer machine which has it's own domain controller. Can view word documents in the browser, editing of docx files stangely works.
FAST previews/thumbails need Office Web Apps running.
Summary: Install Office Web Apps pre AutoSPInstalller is run. Then activate in the autospinstaller. Otherwise install the office web apps but only do the config of the web apps, don't run the SP config wizard.