The most common cause for the Spell/Grammar Check seeming not working is that
the text in document has "Do Not Check Spelling or Grammar" setting applied,
to remove this do the following.
In 2003 and prior:
1. Select all (Ctrl+A to select the whole document).
2. Double click on the language button at the bottom of the Word window (or
Tools, Language, Set Language).
3. Select the Language required in top section of the dialog box.
4. Clear the "Do Not Check Spelling or Grammar" check box. While here also
clear the "Detect language automatically" if this is checked.
5. OK.
The document should now be open to spelling and grammar checking.
In Word 2007, Review tab, Proofing group, Thesaurus, Set Language.
Spell check is a formatting attribute of the text. If you copy formatted
text from another document then the formatting will come with it and if that
include the no proofing option, then that's what you get. You need to either
re-apply the proofing parameter (as described above) or use Paste Special
Unformatted Text so that the formatting of the destination is adopted.
For further details see
http://sbarnhill.mvps.org/WordFAQs/MasterSpellCheck.htm.
Hope this helps
DeanH