Here is the most likely solution to this issue:
FIX:
1. Create a New Message
2. In the To:, CC:, and BCC:, fields, type the name of the offending
distribution list, the one you are using when you get the error.
3. Once the list of DLs is displayed, delete the one that gives you the
problem. You are not actually deleting the list, just the shortcut link to it.
4. Click on the TO, CC or BCC link to bring up the Select Names dialogue.
5. Select the offending DL for the To CC or BCC field and click OK.
6. Send your email
7. next time yo usend email you can type the DL right in on the New Message
page and it will now be linked to the correct DL in the address book.
I certainly agree with the view expressed about the MVP - what a hopeless case......