Core Data application hangs with I try to scroll a Table

Question

I have a little trouble with a Core Data tutorial I am working on. The program hangs if I try to side-scroll a TableView with bound data. There isn't much data in the table at all, maybe 8 or 10 rows only. But every time a scroll I get the spinning beach ball for some seconds.

For the application I have written almost no code. I created the user interface by dragging the data model on the window. The only code I have written is a transformer who calculates the current age of a person from his/her birthday. That is all.

The Table control is inside a SplitView and if I resize the SplitView the application hangs too and the Splitter is difficult to move.