Please try using the latest TESTING version of PMagic for CPUStress (customizing UBCD). There were some bug reports regarding USB devices in some newer versions of the Linux kernel (3.7.x, 3.8.x).
Other possible tests would be:
_ Testing the USB keyboard functionality in other distros with older kernels;
_ "playing around" with USB settings in your BIOS (or UEFI).
In any case, please report back.
Other possible tests would be:
_ Testing the USB keyboard functionality in other distros with older kernels;
_ "playing around" with USB settings in your BIOS (or UEFI).
In any case, please report back.