This problem occurs when trying to open a docx file from within Windows Explorer.
Some docx files have the correct MS 2007 blue "W" icon, others show a plain document icon. If I double click on the plain doc icon, nothing happens. If I right click the plain icon and "Open With\Choose Default Program\Always use the selected program to open this kind of file" is grayed out so I cannot point it to MS Word.
Another symptom that may help in finding a solution is that, when I go to "Control Panel\Default Programs\Set Associations" docx does not appear (docm does).
Finally, when I open a file from within Word, that same duality of some files showing the W icon and others showing the plain icon appears. However, unlike in Windows Explorer, double clicking the plain icon will open the file within Word.
Thanks for the help on the repair. I did that, still have the problem. Then, I got out the disk and did the repair from that, still have the problem.
Some more observations that might help:
)) only the docx files are missing the W icon in both WinExplorer and Word. The doc files are fine.
)) the docx files missing the W icon will not open in Explorer but will open from within Word
)) when I try to open a non-W icon docx file in Explorer, use Open With to try to reset the default program to open it, the option to do so is still grayed out.
Somehow, my instincts tell me that the clue offered by the gray-out may contain the answer as to what has gone wrong.
If this is on the M$ Office side, I could uninstall Office (it's Enterprise 2007, BTW) and reinstall.