Several Outlook 2007 users getting message "Cannot directly book a resource for this meeting" for resources in Exchange 2010

To start, these are NOT set up as true room/resource accounts.  These are user accounts, with other users set up as delegates.

All accounts were able to be booked as resources by all users when we were on Exchange 2007.  We completed moving all but a few accounts over to Exchange 2010 in the past couple of weeks.

The problems started for the few users once the accounts were moved to Exchange 2010.

These particular users do not seem to be able to book any of the various "room" accounts around campus as a resource, they always get the same error message, regardless of their level of permissions to the room.  On some of the rooms they have author level, others reviewer level, and on some no specific permissions.

The majority of users are able to book these same accounts as resources just fine, including those having no specific level of calendar permissions to the accounts.  This only seems to be about 10 users out of 1500+ that can not.

Further complicating the process is that it appears to be very much Outlook client driven.  If any of the users having the problem logs into Outlook Web App, they can book those same accounts as resources just fine.
In Outlook, if they simply list the account in the To: line, and forgo booking the account as the room, the appointment works fine as well.

All accounts in question are on the Exchange 2010 servers now.  

We do have public folders set up on Exchange 2010 as we still have a few lingering accounts that are still using Outlook 2003 that we have not been able to upgrade yet, and had to provide free/busy access for them.

Have ran through the reported "fixes" noted on other threads from un-checking cached mode or checking it, making sure public folders are mounted, and making sure the auto configure is pointing to the Exchange 2010 CAS servers, all appears to be in order.
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You haven't mentioned that you have looked at permissions, try these;

Read: Free/Busy time
Write: Create Items and Edit Own
Delete Items: Own
Other: Folder Visible
pifer-grinnell-eduAuthor Commented:
Yes, I have looked at permissions on the accounts.

On at least 4 of the accounts that these 10 users can not book as a resource, they are listed at author level for the calendar, which would give them all those permissions or above.  They still fail to book the account as a resource.

My account is personally not listed with any specific permissions to the "resource" accounts.  I can book them all as a resource.  As can literally everyone else.

For the users having the problem, it does not seem to matter what level of permission they have set to the resource account.  But again, it only seems to be a problem with the Outlook client.  They can use Outlook Web App successfully and set the account as a resource when booking the meeting.
If you do resolve this, make sure to post!  Good luck
pifer-grinnell-eduAuthor Commented:
Closing this question without resolution

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pifer-grinnell-eduAuthor Commented:
closing this question without resolution.  We are just going to work to convert all of these resource rooms into the new resource room standard and retrain users how to use the neer style rooms
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