Difference between insert a tuple in a table by function and by datasheet

Hi,

this is my 2nd attempt to get some links for my problem.
I don't know whether my question is so stupid or difficult or I'm in the wrong list. Please let me know.

I have the following situation: ( I use MsAccess97 as frontend, ODBC 7.1.0003)
I insert tuples in a table with a plpgsql-function, called in a form via VBA-code. It works fine, but I can't update these tuples in datasheet view. ERROR: an other user has changed in the meantime.....but I'm the only.
When I insert tuples via datasheet view, I can update these tuples, but only these.

I can't see a difference between the tuples inserted by the function and datasheet, but it looks like, that the tuples are *marked*.

Please, give me some information to solve my problem.

Thanks
Irina

E-Mail: i(dot)hasenoehrl(at)aon(dot)at