And now suddenly my Mac has lost the ability to puke HDMI out of the Mini DisplayPort adapter. But if I plug an HDMI-to-DVI adapter into the Mini DisplayPort adapter, it works. When I plug the monitor in through HDMI, I don't even see a "monitor changed" message in system.log, but I do with DVI. I also tried a new Mini DisplayPort-to-HDMI adapter; same.

Given the other video bullshit I've been dealing with, does this suggest my video card is dying?

The Mac is a Mid-2010 27" iMac11,3, and the current line of iMacs aren't all that different, having not been updated since mid-2011, so I was hoping to put off upgrading it until they got around to releasing a new batch. Maybe that's no longer an option.

(That would also mean either downgrading from a 4TB drive to a 3TB drive, or cracking open a brand new iMac, since Apple won't sell you one with a 4TB drive in it.)

Arrrgh.