After upgrading to SEP 12.1 RU4 64-bit, Outlook 2007 stops receiving POP3 emails

I have Windows 7 Home (64-bit), Outlook 2007 SP3, and SEP (unmanaged) installed.

I recently upgraded SEP from 12.1 RU3 to 12.1 RU4.  As soon the update finished, Outlook stopped receiving emails via POP3 (and eventually generates an 0x8004210A error).  Tried reboots, re-installing Outlook and SEP.  

The problem appears to be triggered by SEP's Internet Email Auto-Protect function:  when I turn this function off, Outlook sends/receives successfully; turn the function back on and Outlook stops receiving (but can send).  I have confirmed the inbound/outbound port between Outlook and SEP.

Any suggestions?

JP