Phonebob:
What's happening, is that as you noticed, your Google Chat destination is still referencing the old address. To fix this, temporarily unplug your OBi, then log into your Google account, here:
https://www.google.com/settings/accountMake sure that (as you said) your Gmail account is listed on top, as primary. If you have other email addresses, you can set them as your alternate or recovery email addresses.
Then, go back to your GV account, and go to Settings, on the Phones tab.
https://www.google.com/voice#phonesUn-check and delete the "Google Chat" forwarding destination. Don't worry, we'll get it back. Log out. Log into Gmail this time. Assuming you have the current version of the web browser plugin installed and configured properly, make an outbound call from Gmail. This will restore the Chat forwarding destination to GV, with your Gmail address. Go back to the GV Phones settings page, and put a check mark next to the Chat destination. Plug your OBi back in. That should do it.
If you can't get the calling from Gmail function to work, then do this:
Close all web browsers. Go to Windows Control Panel, Programs and Features. Find and click to uninstall the "Google Talk" entry (yes, it's nuts, but Google Talk is the same plugin as Google Chat). Then, go here to download and install the new plugin, which even more confusingly, is now called the Hangouts plugin.
https://www.google.com/tools/dlpage/hangoutpluginLog back into Gmail, go to Gmail settings, click the "Chat" tab, and configure and test your audio devices (headset or mic and speakers). Now, make the call. If Google asks you to "Try the new Hangouts", do not agree! This breaks calling from Gmail.