Need help with dual screens

Hey guys,
I have been using two monitors for about a year now, and its been great.
Here's whats strange though.
The other day, I switched inputs on my monitor from my PC to my 360. After doing so, the monitor refused to detect my computer (or the other way around).
I have already gone through a ton of troubleshooting, and I am lost now. Here's what I have tried:
Restarted my computer.
Messed with catalyst (catalyst doesnt show a second monitor being active).
Attempted using the DVI-HDMI cable with a different monitor (the cable is fine).
Tried connecting my computer directly to the monitor, bypassing the HDMI switcher I use.

I am out of ideas. One thing I noticed, is when I change to the 360 (connected via the same HDMI switcher) letters appear on the monitor which say "DVI" and when I change to the PC, the letters say "HDMI". Which is completely wrong, of course. It used to do the exact opposite.

My PC specs are:
C2Q 6600 @3ghz
Asus P5Q pro
8gb RAM
Powercolor HD 4870 512mb
One 28" viewsonic (this is the one that isnt working) and a 19" 1280x1024.

Thanks for any help.