Sudden strange display/Quartz problems

So, I'm running 10.7.5 on a 3 year old Mac Pro. About a week ago, I was using one of my two monitors in the living room attached to a different computer. I did a software update while only using one monitor on the Mac Pro, only to find that the one left plugged into the Mac will not work with the second plugged in. It is not a monitor problem, as it works with every other computer in my home. No displays are detected, I've rebooted several times, and this is only the beginning of the problems.

Then, I find that the display will not sleep. If I put the machine to sleep, the only difference is that the mouse is inactive until I click it or hit something on the keyboard.

Then, I try to watch a movie using VLC, only to have an error message come up that my Mac doesn't have Quartz Extreme acceleration, in the error details: "failed to create video output".

Also, if I unplug the monitor that was moved (not plugged into the Pro for a while), then restart with only the crappy monitor (the one that I was using on the Pro solely), nothing is displayed past the grey startup screen.

Any ideas?

(Thanks in advance, I've creeped the forums for ages and have always found what I was looking for, but this is baffling.)

 

Sudden strange display/quartz

The update was Airport Utility 6.2, Java, Safari, Security Update 2013-001, and iTunes 11.0.3.

 

And now, after trying to follow your advice, I get the message "The following disk image couldn't be opened" reason: not recognized.

[UPDATE]: The failure to recognize was due to a bad download. However, now when I try to install it, the installer says that none of my disks meet the requirements.

 

I was pretty sure that was the same Combo I tried to install earlier today, but I tried again just to be sure. And yet again, I got the message that "Mac OS X Update Combined can't be installed on this disk. This volume does not meet the requirements for this update."

 

Positive.

I am running Disk Utility to verify disk permissions, tons of differences in System/Library/Preferences/Displays.prefPane. Will update after repairing permissions.

 

Permissions are strangely irreparable. It will say they are repaired, then I verified again only to find the same set of differences. Apparently, this was a problem for some people when 10.7.5 was first released, most recommend a clean install. I think it might be time to update to Mountain Lion.

 

Thanks for the help!