We have recently started migrating an exchange 2003 network to exchange 2010.
We are now in a mixed mode with about 100 users on exchange 2010 and the rest of the users, about 2500 users, still on exchange 2003.
All our clients use Outlook 2003. When the user is migrated to exchange 2010 they experience problems with opening shared calendars in their favorites. Some calendars open some calendars won't open and the user gets an error stating they do not have sufficient permission to open the calendar folder, or operation failed. They can also get this error if they have opened too many calendars or received an error on attempting anyone of them. The problem occurs for both calendars that reside on exchange 2003 and calendars that reside on exchange 2010 mailboxes Although we can"t find a common denominator for this problem, we have two work arounds. One is have them close and open outlook. They will then regain access to the calendar they were just blocked from before, though they may now be blocked from another"s they just had access to before they closed and opened Outlook. The second one is they delete the calendar which is causing the problem from the favorites and reopen the same calendar in their favorites. Sometimes the problem goes away. But we had cases where the problem persists. Or another calendar gets blocked.
End-users are complaining because there's no real solutions. And we still have to migrate about 2500 users, needless to say that with this problem we can't migrate.
Any help would be appreciated