These issues aren't isolated to word. It is some sort of issue with the back-end driver cbfs.sys. One of the symptoms is that deleted files do not actually delete in a timely manner. This means, that if you attempt to do a delete a file programmatically, followed by programmatically renaming another file to the same name as the just removed file, you'll get a permission denied error because the original file is still in use. I imagine something similar is happening with Word in gator99's case above.
At first I thought it was because of the windows 'FILE_SHARE_DELETE' attribute being specified on the file and that a loose handle was still around. But only boxcryptor's backend should have the file open in the sense that it should be encrypting it or rather removing it on my real filesystem.
Moreover, I saw a bluescreen caused by cbfs.sys when renaming a file a few days ago. All of this started with the given version above.