Could be an EDID or HDCP issue. You got a good start on trying to narrow down where the problem occurs and you might want to keep on that track with things like taking the Kramer switcher out of the path by taking the connection normally connected to its output and connecting the Macbook direct to that. And taking the extender out of the loop by, if possible, connecting the TV direct to the output of the Kramer.
You might also try setting the Macbook for different resolutions and scan rates, especially trying very common ones such as 1024x768 at 60Hz.
The Kramer switcher is VGA/HD15 conectivity, are you VGA/HD15 through the entire signal path? In other words, VGA/HD15 out of the Macbook, VGA/HD15 into and out of the extender and VGA/HD15 into the TV?