OK - I will try to give as much information as possible to reproduce this error.
1. Step
Update CB 1.1 to CB 1.2RC
(I used the expert way to update)
3 Tabs and only 3 fields were in the former 1.1 install.
CB 1.1 Tab and Field Content
Tabs: Login Info, Contact Info, Company Info
Added Fields: Company Name in Company Info;
Title in Contact Info, experience in Contact Info
2. Step
After successful update and db check
going to the next one.
3. Step
Adding some fields to the "Contact Info"
like phone, fax, street, zip, city
4. Step
Recognizing that the fields street, zip and city are in the wrong tab.
5. Step
"Field Management" and edit the field "street". Changed the tab from "Contact Info" to "Company".
6. Step
Doing the same to the fields zip and city.
Both Tab from "Contact Info" to "Company"
7. Now the posted error message shows up and no field saving in the front end is possible any more.
All of the "Tab changed" fields and also some former added fields have to be removed completely. This is the only to get CB work correct again.
Hope you got everything what you need to reproduce this error. I did this 3 times.
For my configuration have look at my initial post.
Many thanks for your response.
Greetings
Andy