'under Idle' here means in a separate process with its own tk loop. I tried from the cmd line and see the same. My 3-yr-old machine has what was then a top-of-the-line Pentium. Also, as I said, the test code works much better than the 6/09 patch with widgets in the frames. Perhaps the demo would work if the two scrollbars and main widget were in a 2x2 grid, with the lower left or right cell left empty, instead of packed.