So, in the middle of working on something, the balance of luminiferous ether in the universe must have come unhinged, because every other column of pixels on my screen went black:

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I tried the usual tricks, to no avail. I figured it was a hardware connector issue, so got an appointment at the Apple store. However, to my annoyance and chagrin, the problem has proved intermittent. It “cures itself” and then recurs. This supported my theory that it was a connector issue, or so I thought.
The Apple Genius, however, taught me a trick to reset the graphics subsystem: shift + control + eject
The last time the problem arose, this trick *did* cure it.
So the question is – is my graphics card going south? Is this some bug in recently installed software (Snow Leopard, the new version of iStat Menus, or Final Cut Express)? Could it be entirely due to my attitude? Or was the reset cure also a coincidence? Only time will tell.