In the latest release if you have a TIBOTable with an OnPostError handler it will never be called; an error dialog will always be shown instead.

I tracked this down to TIB_DataSet.UpdateError, which will call an OnUpdateError handler if defined but otherwise calls HandleInternalException, instead of just raising the exception and allowing it to be trapped by TDataSet.CheckOperation as would have previously been the case.

Easily repeatable by posting a record that violates the primary key and observing that the OnPostError handler isn't called. I can provide sample code if needed.