CY7C68013A locks up stops outputting USB data

We are using the CY7C68013A in a 16 bit slave, write-only mode with the 4 FIFO's concatenated.

Every 2ms data is loaded into the 680 by a DSP with a FrameEnd pulse to trigger the USB.

Normally, in  a noise free environment, the system runs error free.  However when an RF plasma

cauterizing knife is operated in the vicinity of the 680, the USB the USB locks up and stops outputting data.

DSP and other peripherals continue operating properly. The 680's oscillator and ClockOut are still running.

680 requires hard reset to regain operation. All unused inputs are appropriately gnd'ed or tied high.

Any clues as to what might be causing the 680 to latch up?

How vulnerable is the SW loaded into the 680 at enumeration to E-filed radiated noise?

thanks in advance