Welcome to the first Tip Day of 2008!
Problem: You may occasionally find a microsoft word document that claims to have no spelling mistakes in it regardless of the fact that you know darn well that it has. You may check the language settings and find that it is set to the correct language and uses the correct dictionary, and you may reset the spell-check and ask it to recheck the document. And you may still find spelling mistakes in it. Really obvious ones. This is most likely to happen if you are using versions of Microsoft Office from 2003 or later but can still happen with Office 97.
Solution: Get yourself a copy of Open Office. Open the document in Open Office, select all the text, and right-click it. Choose “character” from the menu and look in the font tab. Check that the correct language is set (you’ll probably find that there is no language set at all) and click OK. Save the document and open it up again in word and you should find that it now picks up spelling mistakes and grammar again.
Cause: We think this is something to do with MS Word having the ability to set languages at the level of individual paragraphs, but have yet to figure out why it should happen to a perfectly normal document for no reason… that’s MS Office for you!