Test-OutlookWebServices with the -ClientAccessServer switch to test your AutoDiscover Services.
(Taken from this great article: http://blogs.dirteam.com/blogs/sanderberkouwer/archive/2007/03/10/exchange-server-2007-and-the-active-directory-part-5.aspx ).

Tests using: http://www.testexchangeconnectivity.com/  show the following error:

"rpc_s_server_unavailable error 0x6ba was thrown by the rpc runtime"

You will probably also see the following error in your Application Event log on the Exchange server:

NSPI Proxy listen port on transport Rpc/HTTP (v6) is being overridden by registry setting System\Current Control Set\Services\MSExchangeSA\Parameters\Rpc/HTTP NSPI Port.  NSPI Proxy will listen on port 6004 on this transport.
Event ID: 9091

Other symptoms:

Outlook 2003 or 2007 will not connect from outside the network using the proxy address you have set up, you will be prompted for password multiple times, you will not get name underlinedor server underlined in Outlook mail account setup.

If you have another Exchange 2007 in the organisation at a different address, it may use that and connect instead, this is a workaround, (assuming that server doesn't have the same issue).

Autodiscover appears to be working fine.