New Mac Pro Headphone Jack - Was Working, Now Screeching/Feedback Sound?

Anyone knw what is wrong here? I plugged my new Sony headphone/monitors in to the Mac Pro like I've done every day since i got it a week or two ago, and it just has this horrible screeching/static sound coming out of the headphones?

Any ideas?

Can you get it to an Apple store for them to check out? Could be a bad port. But, could also be bad settings somewhere. Review the audio settings everywhere. System Prefs, etc. Sounds like something is overloading something in the audio stream somewhere. Check volume levels everywhere, too.