[SOLVED] Error: Gateway Not Selected - users can't register

I've been using Community Builder on a live site for a while but I'm still learning so haven't activated most of the features yet. The user manager has been active for some time and has been working fine until last week. When users try to register they get the error message "Gateway not selected". If you refresh the page it appears to go through, the confirmation email is sent but when you click on the link in it, the page says you cannot view this as you are not logged in. OK so you log in and get the message that your registration is not complete, please confirm your email. Another confirmation email is sent and the cycle continues.
In the back end, the new registered user does appear as unconfirmed. If I try to edit the user's profile, I get the same Gateway Not Selected error.
As I said, it's been working fine for months up to now but a few weeks ago I started adding more plugins and updated everything. I did notice there were three CB login modules, one original,one added automatically when I migrated from Joomla 2.5 to 3.0 and another added automatically when I updated CB. Only one was published, I tried publishing them all, that seemed to get rid of the Gateway thing but not the email verification issue - maybe one won't verify the other, I don't know. I eventually trashed the two later ones I was not using. The problem persists.
The whole thing is a mess, I have over a dozen new users who are frustrated. What do I do?

Sorry, forgot to mention, the site is www.vibrations.ca using Joomla 3.3.6 and CB 1.9.1, Joomla login module is turned off.

I've no idea what "Gateway not selected" is coming from. I'm not finding such a string anywhere in CB or our plugins. If publishing all of CBs plugins gets rid of it then you probably have a 3rd party plugin incompatibility issue. You'll need to review and re-test all of your non-core CB plugins and see which is causing it.

Thanks Kyle - I don't have any third party plug-ins though the problem did start when I upgraded my membership and, like a lottery winner on a shopping spree, started adding just about everything you offer. What I published was not all the plug ins but the three CB login modules and I'm not positive what effect that had because simply refreshing the page does the same thing.
Also, I see I misread the error, it is actually "Gateway has not been selected". The message doesn't come up in the standard Joomla error area, it is a pop-up message box. If it helps, here is a screen shot.

If I click OK and refresh the page (without filling in the empty fields) I get this:


I email is sent but I get the vicious cycle, the link takes me to a page that says I must log in, I try, but get the message my email hasn't been confirmed.

My site isn't huge but it is a big part of my business and it has two busy seasons in the year, one of them is this week. I am having several people trying to register every day and they can't, I fear they are lost forever.
Would it help if I just re-load CB?

OK I'm thinking this has something to do with that Invite Code field on the form. I have not found a use for it or a way to get rid of it. I do have JEvents which is supposed to work with CB - maybe that is the issue. Should I take it to them?

Issue resolved. It was another component, not one related to CB but it did interact with users (and didn't work).
Thank you for your time and quick response, I'm sure I'll need you again.