Ethernet Shield - Severe VHF RFI

I have an Arduino Uno with Arduino Ethernet Shield. I have successfully set it up to control RGB LED lights in my room but I'm having some serious problems with RFI in the VHF band when an Ethernet cable has been plugged in for a short bit. I can make the interference go away immediately upon unplugging the network cable at either end. I know it's not my network switch because I have a VoIP adapter that does not exhibit these problems linked at the same 100Mbps on the same network switch with the same network cable. It only happens when the Arduino is connected.

This interference makes radio communications completely unusable (jammed at S9 within 20 feet, S3-S4 interference even 100 feet away in the parkinglot on 145.270, 146.520, and possibly other frequencies that I'm not aware of yet.

Is there anyone else that is having issues with RFI from an Arduino? How can I resolve this?

I found some information on another site which complained about the same problem with Linksys routers (mine are GreenNET gigabit switches in shielded metal cases) but can't figure out how to force the Arduino into 10Mbps mode as the article suggests to mitigate the problem. RF chokes on the cat5 cable has helped but not completely resolved the problems.