I've noticed that AO's Spell Check feature doesn't work very well (at least not with IE). If you would like a client-side spell checker than you can use the little htm file that I have attached. If you are running under any Windows version and MS Word installed on your PC here's what you need to do to install it:

[list=1][*]Copy the SpellCheck.htm file to any convenient folder[*]Run regedit (I suggest you make a backup copy of the registry before you begin)[*]Navigate to HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\MenuExt[*]Add a new Key named Spell Check (or anything else you want to call it)[*]Click on the Default, right click, and choose Modify[*]Enter the path to SpellCheck.htm (e.g. C:\htm files\SpellCheck.htm)[*]Right click on the Spell Check key and choose New|Binary Value[*]Change the name of that value to contexts[*]Right click on contexts, choose Modify and type in 04[*]Restart AO, highlight the text in a post that you want to spell check, right click, and choose Spell Check.
Note: Under some operating systems, the little spell check window gets hidden behind other open windows but it's not hard to find.