This seems more of an ODBC issue than an Excel issue. So I think it depends not only on the SQL Server side, but also on the ODBC-driver that's used on the client side (XP, Vista, Windows 7).

If you can't find out in the documentation, this is typically a question to ask your Microsoft support. After all, they wrote that driver and it's their database. So if anybody knows, it's them.
Companies that have fail-over service surely have the right support contract with Microsoft to get this issue solved in a wink.

Can you tell us the solution once Microsoft told you? It might be interesting for some other members.

Kees