Need help with new iMac and TV

I'll try to explain the issue as clear as possible.

I have a gaming setup, HD TV, Happauge HD PVR, PS3/Xbox. The HDPVR records the visuals on the TV to my iMac with the program Elgato Eyetv.
I had previously run this setup with my laptop and everything ran smoothly (and still does)
This same exact setup with a new iMac has issues however.

As soon as I plug the USB (from the HD PVR) into my Imac, I receive a feedback noise coming from my TV. In addition to this, I am also visually seeing red/green lines across the TV moving upwards on my TV Screen.

Neither the Feedback Noise nor the Visuals are communicated through the iMac however. thus, my recordings are normal (good audio/visual) however, this issue makes for a poor viewing experience on my tv.

I've tried switching all cables, it seems as if the cables are not the problem, (considering the setup works on my macbook) it seems as if something is wrong with the iMac itself

I called AppleCare and they weren't able to help.
I did a PRAM reset (i think it's called) and had no success, they suggested I contact the EYETv program, but i know it has nothing to do with that (the color distortion and feedback both exist without the EYETV program being opened.

Simply plugging the USB from the PVR into the Imac causes this problem.
and yes, Ive tried different USBs.

Any insight or ideas would be greatly appreciated.