Trouble with OpenID and Google Login

I upgraded my forum from 2.0.17.10 to 2.0.18.1 a few days ago with no real trouble, but since then my users have been reporting odd behavior when logging in through OpenID or Google:
When I log in via Google it logs in okay (I appear logged in on the top menu bar) but it takes me to the log in page where you normally put your user name and password.
The same thing happens with Open ID log in when I use Yahoo.com. After I enter the requested info, a screen comes up with my user name and password. When I press the sign in button from that screen, I get a message telling me I am not signed in and user name/password is incorrect, not registered. I just go to the forum menu at the top of the page and I can access the boards.
It seems they're successfully logged in, but they're no longer returned to the forum homepage like before, rather they're being sent to the Vanilla login page. Has anyone else experienced this? Could it be related to my custom theme? I'm guessing not...
Any assistance would be appreciated!
Answers
Have you copied over the new openid from the upgrade?
grep is your friend.
Thanks for the response @x00, the forum is indeed running the latest OpenID plugin files.