Just about every day PacketCapture.exe faults and then is followed by a string of NtxDrv errors

We have DLP 11.6.2 set up on a Win Server 2008 R2 64 bit box.  Originally we were going to use Endace cards until we found out they weren't supported and so switched to the napatech cards.  Pretty much since we got these boxes up and running a few months ago on the one of our two monitor boxes we've been getting PacketCapture faulting followed by a string of 4 - 7 NtxDrv errors.  Googling it doesn't reveal anything and I thought it might've been that we still had the Endace drivers installed but they're gone so there goes that theory.  Anyone have any idea what NtxDrv is?