Leopard Graphics Update does a de-rez on external displays
Imagine the scary, Sarkian voice of David Warner intoning "You will be subject to immediate de-resolution" and you'll know how a cluster of Leopard-using laptop owners (including yours truly) are feeling after getting bitten by a problem in the Leopard Graphics Update. You can see the rundown over at MacFixIt; the symptom is that after a restart or crash, the previously-happy external display is registered by the OS as a replica of the internal LCD, limited to the same 1400x900 resolution (in the case of the MacBook Pro 15" I'm using) as the built-in display. Custom calibrations and other display-specific tweaks are also nowhere to be found.
The usual first steps to troubleshooting display issues -- unplug/replug, "Detect Displays," sleep and wake the laptop -- were fruitless. For me, even the heroic measures of a PRAM reset and deleting the com.apple.displays plist from the ByHost preferences folder didn't make a dent. Switching from a DVI to VGA cable left me with only a secondary screen on the laptop, sans menu bar, and the usual Cmd-F2 to trigger a display detect did nothing at all. How aggravating!
Still, one of the reasons I heart MacFixIt is because there's usually an offbeat (not to say wacky) workaround in the mix when a problem comes on the radar. In this case, the suggestion that made me go "Wha? Nah!" was to power on the laptop, immediately close the lid (with external display still attached) and wait for the machine to boot completely. I tried it; lo and behold, the external display is now recognized correctly, and when the machine is slept and awakened or "Detect Displays" is triggered, everything behaves as expected.
Sometimes, when the weirdest possible fix is the one that works, you just have to put the laptop down and slowly back away.
