CRED form can't be upgraded

Hello,

I use latest TVC plugins with WP 3.5.1.
I created a CRED create form which belongs to a custom post type created by Types.
I used <Scaffold> to generate specific code. I removed some items from code checking <Preview> ( it was what I want ) and wanted to upgrade this CRED form.
I was not able to save it.
I had 2 CRED forms created earlier but I deleted them all before trying to create this new one which I'm not able to save / upgrade.
I do it in Chrome.
Thanks,
A