Only an info and hopefully usefull for others that run into this problem. It took me some time to figure it out because there are no errors in the logfiles.
It seems that SWFtools 9.2 have some bug or something really new that Alfresco can't work with. Word files are not previewed correctly. First I thought that openoffice is converting the doc and docx files not correctly and upgraded to OpenOffice 3.3. But it didn't help. After downgrading my SWFtools to 9.1 everything is displayed correctly in the preview.
