ASUS P8P67 Intermittent Recognizing of Speakers

So here's the gist of my problem: When my speakers are plugged in, it seems like my motherboard is constantly recognizing, then unrecognizing my speakers. I'll get messages every second or so saying either "New audio device plugged in" or "Audio device unplugged".

Because of this (I assume?), I can't get any sound to play out of my speakers.

Computer is able to recognize a USB headseat/mic fine and I can hear sound out of it. Just stuff plugged into the little green jack in the back seems to be having this problem.

(May or may not be relevant) - Everything worked fine up until a few days ago (I've had the P8P67 for about 1.5 months) when suddenly my computer wouldn't recognize anything I said into my USB wireless headset. I still actually can't seem to use my headset to talk, but I can use it to hear things.

System Specs to help troubleshoot:
P8P67 Pro
i5-2500k
ATI Radeon 5870 x2 (running independently, not crossfired)
8GB G Skill Ripjaws X DDR3 1600 CL8
Rosewill 1000W power supply
Crucial C300 120GB SSD

I've been running my computer under pretty heavy load (GPU and CPU at about 100%) for the last few weeks. Could that have caused something in the board to short out?

I tried uninstalling, then re-installing the realtek audio drivers last night, but that didn't seem to help. Do you think this is more a software (drivers) problem or a hardware (actual motherboard) problem? Any ideas?