sorry.. but seems not reproducible for me at RichFAces sample (FF 3).. could you please add more details like code and browser used.
Found the solution:
My extendedDataTable columns and their content are dynamically build based on database fields.
So my column ids are like "Field Name"+"Col"
As some field names contain "_" character, this is generating weird behaviour of EDT columns.
In the future, for sure (considering the time I spent to find this!!), I will not put any JSF id with special caracters like "_", "-","."...etc
Is that specification taht JSF id must only contain letter and numbers?