Outlook2k7 with Exchange2k - repeated failed login

[TMBarnhart]

We are in the process of migrating our users from Exchange2000 to Exchange2007.

99% of my 5000-users are on Outlook2k or Outlook2k3.

Outlook2k and Outlook2k3 can see both the Exchange2k and Exchange2k7
mailboxes.

My 1% on Outlook2k7 love Exchange2k7, but cannot access the mailboxes still
on Exchange2k.

For example, we get a repeated login request (from the Exchange2k7 server)
when they try to access a user's calendar on the Exchange2k server...

I've found numerous mentions of this on the web & forums that discuss it -
but no solutions.

Does anyone have a solution to this...?

 

[TMBarnhart]

Further info about our configs...

1) All of the Exch2k7 CCR-Mailbox Servers and HUB/CAS servers are in the
same domain and same site as the Exch2k servers.

2) All Exch2k7 are at SP1, and Exch2k are at the post-sp3 rollup.

 

[TMBarnhart]

Further info about our configs...

1) All of the Exch2k7 CCR-Mailbox Servers and HUB/CAS servers are in the
same domain and same site as the Exch2k servers.

2) All Exch2k7 are at SP1, and Exch2k are at the post-sp3 rollup.