Arduino constantly rebooting when connected to USB

I am a little baffled by this one. My 3DoF rig has been performing well but lately I had to reset things to make it work and have the game engine actually connect to the rig.

The last 2 days I've been unable to actually get the rig to respond to game engine commands and first I brushed it off as likely a USB conflict or overloaded USB bus. I have attempted the following so far with no luck:

1. Turned off any other devices on the rig
2. Used a different USB cables
3. Powered the arduino manually through a power usb adapter and through a PSU
4. Installed an additional USB expansion board dedicated to the Simtools Arduino
5. Assigned a different com port
6. Installed ferrite beads on the USB cables

The rig boots up fine but it looks like the arduino reboots (my motors drop before going back to the default position) every 5-10 seconds. If I just let the rig boot up without connecting to the computer / USB it actually stays stable and doesn't reboot (i.e. engines don't drop). That seems to rule out a PSU problem and really points at the connection to the computer. Any suggestions?

I'm actually using a different controller, not just a different port. I purchased and installed a separate PCI USB controller to exclude this problem.

Edit: the issue also occurs when the Arduino is the only USB device attached so likely a bus overload isn't happening

It has to be something on the computer. I hooked up an older laptop which has the copy of SMC on it that I tested the rig out with last year an I'm perfectly able to control it. Something is goofy.