Cannot import *.docx files to pdf

Running Windows 7 Pro 64b. Have Acrobat Pro X.

For several years, I have been adding files by clicking "Combine files into single pdf". I can no longer do this with Word (*.docx) files. I now get error message on the Combine Files box: "Cannot convert file type to PDF. Please remove this file from the list. "

Not sure what happened. For a new job, I did install OpenOffice which has SWriter (*.odt files), the Microsoft Word emulator. Not sure if this had anything to do with it.

I can still print to a PDF file. But that takes time. I do a lot of combining of files I create. Much easier to drag and drop into the Combine Files box.

Thanks - in advance - for your help! I'm stuck on this one.

Michael Workman