That's strange. Do you have both 2007 and 2010 installed? Do you perhaps have the x64 version of Office installed?
Can you try the following?
- Create a new blank project (not based on a Word document).
- Go to File > Import > Word document.
Can you import .docx from there?
That is the other bizarre part. When I create a new project, it will let me choose a .docx file to import only as the first page of the project. Even if I start if off with the .docx file or a blank project, adding (linking or importing) any additional Word Documents only gives me the *.doc and *.rtf.
I have only Microsoft Office 2010 suite 32-bit installed.
When you go to open a document in an existing project as in your first image your dialog is only showing DOC and RTF whereas in the second image all the required options are showing. So the question has to be what is different and one possibility is that in the first you are browsing to a network and in the second you are browsing locally.
Try copying the document you were trying to link to / import to your local drive and then try to link. Are the options then different? If yes, I would suggest a chat with your network guys.
Let us know how that goes.
See www.grainge.org for RoboHelp and Authoring tips
All folders, local and network show the same options for file type .doc and .rtf.
However, I did find a slow workaround. If is simply type in my file name with the correct type, it will link to .docx files successfully and update when needed. It is just a little more tedious than selecting them from the list.