I was going to ask a question, but in doing further research I answered it myself. I will post the results of my findings here in case someone may find it helpful.
My colleague replaced his XP desktop with a new machine running Windows 7. In setting it up, he installed a newer version (the latest at that time) of OpenVPN than was previously running. This machine acts as a site-to-site VPN, connecting his home network (including his VOIP phone) to our office. He installed OpenVPN 2.1.4 -- released on 2010.11.09. The VPN seemed to be setup properly, and while I could see traffic flowing from the phone to the phone system and back, the second packet sent by the phone to the phone system was not getting to the office side of the VPN. Once I used Wireshark and discovered the packet WAS being sent on the OpenVPN NIC, but was not being received on the other side, I figured out this was 99.999% surely an OpenVPN issue.
I was going to have him try going back a version of OpenVPN, and hope it ran ok in Windows 7, but when I looked at the site today, I see a newer version still was released recently: OpenVPN 2.2.2 -- released on 2011.12.22. My colleague installed this version right over the old, the config folder left intact, and voila, the missing packet now gets through, and the phone is working once again.
Bottom line - at least if you are using NEC Aspire and VOIP phones offsite with OpenVPN site-to-site connecting them, watch out for version 2.1.4, at least on Windows, there is definitely a bug there.
