OSX 10.12 won't detect VGA monitor after plugging in HDMI TV

I have a GTX 660 TI, with nVidia web drivers installed, and a VGA monitor plugged in using a DVI-VGA passive adapter, which worked fine the first day of using my new install.

But then after re-plugging in my TV, OSX stopped recognizing the VGA monitor after boot, even when I tried booting with the TV unplugged.

Notably, the boot text does work fine on the VGA monitor, right up to the point where it asks for the login password.

Is there anything I can try?