TBC Classic Era (Vanilla) and TBC Classic Era are currently available. They are two separate clients. You can't create characters in both. The WOW TBC Gold version that you're currently working with is the one that you were using before.
They updated the "Classic" client on TBC to implement the initial change from Vanilla to TBC. They added "Classic Era" as a download option. They also made the update. All characters were copied to "Classic Era", both the "current" version of the character and cheap Burning Crusade Classic Gold the "Classic Era" version were removed. The next step was to choose which version to activate, which would block you of the other (the vast majority of users activated the TBC version).