A buzzing problem with my microphone

Factual Questions
1

My problem involves an annoying buzzing sound that people hear when I talk to them in Teamspeak, but ONLY when I’m running a game. Otherwise, I sound fine.

A couple days ago, I got into TS and talked with my clan-mates. I sound fine, they sound fine. After awhile, I load up Bad Company 2, and they tell me they now hear a buzzing, electrical-interference-type sound in addition to my voice. According to them, it got worse and was really bothersome, then at other times it was less bothersome. It’s been described as “bees”, or “a vibrator”. A lot of fun was had with the last description. Since then, I’ve verified that other games also cause this issue.

I fiddled with different settings in Windows and in TS3, but nothing helped. I rebooted, no luck. I deleted my sound drivers, went to my motherboard site and got the latest audio drivers (turned out I was already using the latest drivers), rebooted and reinstalled. No luck. I tried a different set of headphones/mic. Didn’t help.

The only thing I can think of that’s different between when my mic worked and when it didn’t is that Windows automatically updated. I didn’t unplug anything, I didn’t move wires (I DID check the plugs and wires AFTER the problem occurred.) I didn’t install any other new software or hardware. As a test, I restored my system to a time earlier than the Windows updates. It did not solve the problem either.

So, to some up: 2 sets of headphones/mics (different brands, both using 3.5 mm plugs) checked, audio drivers removed and latest audio drivers reinstalled, system restore done. Nothing helped.

My system:
Windows 7 Pro - 64-bit
i5-2500k (about a month old)
GTS 250 video card (about 4 years old)
[KINGWIN ABT-450MM 450W](http://www.newegg.com/Product/Product.aspx?Item=N82E16817121024) (about 3 years old)   
4 gigs RAM (about a month old)
I'm using on-board sound: [Gigabyte GA-Z68P-DS3 (with Realtek ALC889)](http://www.gigabyte.com/products/product-page.aspx?pid=3899#sp)
Logitech h150 headset/mic (not usb-style, but the 3.5mm plugs)

The only thing I can thing of is that some piece of hardware is going, but what? Is it the graphics card? Is it the power supply? It seems like something is being taxed by going into a game, as the buzzing problem does not occur outside games.

2

A sticky problem, huh? Well, here’s my single ‘bump’. Someone on another board thinks it might be my power supply, and that’s the direction I’ve been leaning all along. I didn’t want to bring that up, so as not to plant the idea in anyone’s head and steer the conversation, but since I’ve got no responses, I might as well do it now. A 3-year-old PS, fairly small, not the best brand (though with good reviews at NewEgg) and newly stressed due to a more powerful CPU. . .it’s the best guess I’ve got.