I'm using this plug-in on an older site, and yesterday we noticed that we couldn't update any GCBs or add new ones, despite the plug-in saying it had.
The first thing I did was update the plug-in. No change.
I then updated WordPress from 3.2.1 (I think) to the latest. No change.
I then created a new site with a fresh install of WP and added the latest GCB. Works fine. Hmmm.
On the problematic site, I've updated other plug-ins and that hasn't helped.
Further to this, I exported the GCBs from the problematic site and imported them into the new site to check that they weren't the problem. They worked fine, but I noticed that their IDs had completely changed. For example, ID 459 had become 259. This would be a real problem had I have removed them from the problematic site and re-imported them.