This is always funny. It's usually a user trying to spell something like "theatre." Lotus Notes puts a red line under the text. Then they complain that Notes can't spell and write off the spell checker as incorrect.
The culprit? Their dictionary is on English (US).
Here in Canada (and virtually everywhere else outside the US that uses a variation of English), theatre is spelled with a "re" instead of with an "er." US English spells "color" and "flavor" while we spell them "colour" and "flavour," and so on.
It's funny, I also saw someone complaining that Notes kept marking English US words as wrong, even though his language settings in Lotus Notes were in his native Dutch. Of course it is. Try finding an unmodified Dutch language spell checker in any piece of software to mark "statuatory" as correct and proper Dutch, and I'll switch to Outlook for you.
Please make sure your users are on the correct language.