Read-only document from SharePoint displays “Check Out” option

I don't like to post issues without solutions, but a client alerted me to this one today and I couldn't find an answer; I wanted to put it out there in the hope that someone can offer some input. Here's the scenario:

In your MOSS 2007 or WSS 3.0 implementation, you have a document library with checkin / checkout enabled. If a user with read-only ("Visitor") permissions looks at the document options from the drop-down menu on the document name, they have no option to check in or check out:

However, if the same user opens a document from that library, the document will open as read-only in its MS Office application (Word, Excel, etc.), but the user will see the "Server Document" bar with the message "To modify this document, you must check it out" and the "check out" button.

When the user tries to check the document out, they are asked to authenticate, they try three times, and then receive the error "Cannot perform this operation. The file has been deleted or someone else has it checked out."

The good news is that the application won't actually let you check out the document – it knows you shouldn't be able to authenticate.  The bad part is that that toolbar shows up at all, and the user has to go through the authentication / bogus error process.  How is it possible to prevent a user with read-only rights in SharePoint from seeing the "Check out" option in Word or Excel?

I posted this to the MSDN forum for Sharepoint general questions. (I've got a private bet with myself that someone will tell me this is supposed to be posted to an MS Word discussion group instead.)