I know something typed on notepad etc can't be opened on Word. Could it be the document was not typed on a format compatible with Word? Just a guess
Here's MS's take
http://support.microsoft.com/kb/822645#kb1
have fun
first scan it for viruses. then open it using the file filter "recover data from any file". you may not see formatting with it, however.
p.
Was the particular document made with your copy of that program or are you importing it?
If you imported it, then from what program?
Could be a corrupted file.