Auzentech HT HD Buzzing ... Until I Remove the Bracket

Hi all. Same ol' sob story: My GPU (BFG GTX 285) under load is causing my sound card (Auzentech Home Theatre HD 7.1) to buzz. The odd thing is, if I remove the bracket (the back plate) and reseat the sound card with no support other than the slot, the buzzing stops. So I can only assume whatever EMI the GPU is causing is being transferred to the sound card via contact with the case.

I wonder, what could be causing this? I know it's an issue with the GPU because the 285 makes an audible buzz when under load, the higher the FPS the louder the buzz. It matches the sound I'm hearing perfectly, both in pitch and volume (which varies when the load changes). I can hear the buzz both in my headphones and on my speakers. I have the Auzentech seated in the only available PCI-e slot on my mobo, right beneath the GPU (there are no other PCI-e slots that can accommodate it), so I cannot relocate it away from the video card.

Any thoughts? I've tried electrical tape and even painting the bracket to isolate it from the case, but all attempts have failed. I seriously wish I could located the root of the issue, whatever is enabling my GPU to broadcast the interference via the case. I obviously cannot leave the card installed without a bracket, not if I ever want to stand my tower up again. Does this indicate that something, somewhere isn't grounded properly?