I have encountered the same error through a quite different path, but I think it is likely this solution will fix yours as well.
How the problem manifested for me:
- Open Word 2007.
- Load any document.
- Open file properties (File > Prepare > Properties).
At that point I received a message "The document information panel was unable to load."
The fix:
Copy IPEDINTL.DLL
from C:\Program Files\Microsoft Web Designer Tools\Office12\1033
to C:\Program Files\Microsoft Office\Office12\1033
Comments:
This is apparently a file associated with InfoPath (which I did not install when I installed Office 2007) yet it strangely fixes this issue with Word (and apparently Excel from what I have read).
By the way, the credit for the fix goes to Tom Van Gaever; I am just the messenger here.
2010.03.10 Update
I confirmed that this defect manifests by not installing InfoPath in the Office 2007 bundle: on a separate machine where InfoPath was installed the error did not occur.