From TechNet - edited to fit.
Q241485 modified on 03-01-2001:
The information in this article applies to:
-MS Outlook 2000
CAUSE
-MS Office shared Proofing Tools aren't installed.
-spell checking isn't configured properly.
-The insertionpoint isn't in the message body when you spell check.
RESOLUTION
1. Verify the configuration of the spelling checker. Click Tools, Options, Spelling tab. Make sure "Always suggest ..." & "Always check ..." are checked.
2. If General Options arn't active on the Spelling tab, quit Outlook. Click Start, Settings, Control Panel.
3. Double-click Add/Remove Programs. Select MS Office 2000 or MS Outlook 2000, and click Add/Remove.
4. Click Office Tools tree, Proofing Tools, Spelling Checker. Make sure it's set to "Run from My Computer".
If it's set, click the Spelling Checker, and then Update Now to reinstall it.
5. When the process is complete, reboot. Start Outlook and type a misspelled message. Try to send it to see if spell checker works.
MORE INFORMATION
If you install Office 2k and do not install the proofing tools, the spelling checker isn't available to Outlook and the error occurs.
To Install the Proofing Tools
1. Click Start, Settings, Control Panel.
2. Double-click Add/Remove Programs.
3. Click MS Office 2k / MS Outlook 2k and Add/Remove.
4. In Maintenance Mode, click Add or Remove Features.
5. In Update Features, click (+) at Office Tools. Click Proofing Tools, Run From My Computer, Update Now.
Selecting a Custom Dictionary
The error may occur if no Custom Dictionary is defined. To select one:
1. In Microsoft Word, click Tools, Options, Spelling and Grammar tab, Dictionaries.
2. Ensure that a check is next to Custom.dic. Click OK, OK, OK.
3.If one isn't defined, click Add and name the new dictionary. Click OK. Go back to step 2. Create a message and see if it works.
Copyright Microsoft Corporation 2001.
