Problem:

Client is attempting to access Outlook Web Access (OWA) and are returned the following error after login attempt:
A problem occurred while trying to use your mailbox. Please contact technical support for your organization.
and/or
An unexpected error occurred and your request couldnt be handled.

Cause:

This issue occurs when the msExchVersion attribute is not set correctly on the user object in the Active Directory. Exchange 2007 uses the msExchVersion attribute to determine the version of Exchange that user objects are associated with. If the version value is less than 0.1, Exchange 2007 considers the object “read-only” and cannot write changes to the object.

Solution:

From the Exchange Management Shell execute the following command:
Set-Mailbox -Id "Domain\ID" -ApplyMandatoryProperties

To verify the adjustments you can use the Get-Mailbox command:
Get-Mailbox -Id "Domain\ID" | FL ExchangeVersion