Upgraded to Mavericks, mini-displayport vga no longer works So yesterday I decided to perform the free upgrade to Mavericks, but when I came back today to use my computer, my external projector no longer gets a signal from my iMac. I can verify that the signal is going out, as the display is black, rather than showing "no signal," but all it gets is a black screen.

It also only shows a black screen in the display preferences.



I've tried changing to a scaled resolution, resetting the PRAM, and simply switching mini-displayports, but nothing will make the display turn on.

Any ideas?
If you reset the NVRAM and then boot to the recovery HD you should be able to tell if the problem is hardware or software without needing to boot from the older OS.