Password prompts - Exchange 2013 RTM vs. [Outlook 2007 & Outlook 2010] - Fully patched

Exchange 2013 RTM  - Multi-Tenant

ExternalClientAuthenticationMethod : Ntlm
InternalClientAuthenticationMethod : Ntlm
IISAuthenticationMethods           : {Basic, Ntlm, Negotiate}

Clients using Outlook Anywhere only, not Exchange domain members.
1. Windows XP SP3 (fully patched), Outlook 2007 SP3 + Nov 2012 Patch - When launching Outlook prompts for password only once.
2. Windows 7 (fully patched), Outlook 2010 (fully patched) - When launching Outlook doesn't prompt for password.

I'm aware of this:
http://support.microsoft.com/kb/956531

The goal - Eliminate issue with password prompts for Windows XP.

Any chance resolving this? CU install? Anything else?

Thanks.

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Memento Mori