Losing Access to Additional Mailboxes

I have clients who need to have access to shared and other user mailboxes. I go through the Powershell procedure to grant the users full access, and send as access as necessary to the mailboxes and they then automatically appear as an account below the user’s mailbox folders within Outlook 2007 and Outlook 2010.

Every so often a user will lose access to a mailbox that they have full access permissions on, Outlook 2007 reports that that it cannot display the folders whereas Outlook 2010 will stop updating the folders leaving you with access only to the previously cached folders and emails.

This happens randomly to users using Outlook 2007 and Outlook 2010. There appears to be no pattern to it, different users are affected at different times and it happens across different clients. I have contacted Microsoft support on various occasions and it never comes across as a known issue to them. The only way I have found to fix the issue is to recreate the Outlook profile for the user which is a pain as it seems to happen to a few users per month. I can even reuse the old Outlook profiles OST file by deleting the newly created one and renaming the old one. Once this is done the additional mailboxes are properly accessible if using Outlook 2007 and if using Outlook 2010 emails from the additional mailboxes start being cached again.

Any help or advice would be appreciated.

Thanks very much.