Cannot connect to Exchange 2000 on Vista

I'm unable to connect to an Exchange 2000 server via Outlook 2007/2003
on Vista. The problem is specifically linked to the OS and not the
Outlook client, since connections to the same server on Outlook on a
different OS (Windows XP Professional) work fine. I have tried both
Outlook 2007 and Outlook 2003 on Vista and they are unable to
connect.
I'm able to ping successfully to the Exchange Server from the command
prompt. However, when I try to set up the Exchange account in Outlook,
the mail setup fails after I click "Check Name" saying that the server
cannot be accessed. (It's a regular Exchange 2000 connection. There's
no RPC over HTTP)
I have tried disabling firewalls, and UAC, but that doesn't seem to
make any difference. I've also tried a fresh install of both Outlook
and Vista, but no dice.
As I mentioned earlier, I'm able to connect using Win XP. Even more
infuriatingly, if I run VMWare or Microsoft Virtual Machine inside the
Vista OS, and then run Windows XP and Outlook on the Virtual Machine,
it's able to successfully connect to the Exchange Server!

Please help!

What version of Vista?

What version of Vista?  I assume the Vista edition is Business, Enterprise
or Ultimate so its joined to your domain?

--
John Oliver, Jr
MCSE, MCT, CCNA
Exchange MVP 2007
Microsoft Certified Partner

Cannot connect to Exchange 2000 on Vista

it is Vista Business and yes, it is joined to the domain

Can you start Outlook from Run Command, outlook /rpcdiag?

Can you start Outlook from Run Command, outlook /rpcdiag?  Can you post
results?

--
John Oliver, Jr
MCSE, MCT, CCNA
Exchange MVP 2007
Microsoft Certified Partner