DAQ Pad 6508 loses its configuration...anyone know of any possible reasons?

[REash]

Hello,
 
I'm using a NI DAQ Pad 6508 in a LabVIEW application.  I am using all ports as outputs to a relay card.  My 6508 device "locks up" at seemingly random times.  By "locking up", I mean that the 6508 loses it configuration (the green LED on it shuts off), and it is "locked" into the last output state prior to the "lockup".  This causes my relay card to freeze at that last state.  The 6508 will return to normal state after cycling power or unplugging and replugging in the USB cable.  Does anyone know of any possible reasons for why this could happen to the 6508?
 
Thanks!
Ryan

[REash]

Michael,

I did see that thread when I was searching for an answer, but that does not seem to pertain to me.
As I stated in my previous post, I am using two of these devices, and
the one that keeps losing connection to the PC is always the one
connected to a certain bank of 4 relay cards on its outputs.  So
it is NOT the same DAQPad that is failing all the time.
So I was wondering if there was a problem with one of the relay cards
which could somehow cause the 6508 to lose connection with the PC (and
how would that be possible?), or if my LabVIEW program has some problem
in a section of code that uses those relay cards which could cause this
problem (again, is that even possible?).  I am currently swapping
the relay cards out one at a time to see if one of them is causing
this.  The bad thing is that the problem is so random and can take
hours to appear, so the process of going through each relay card is
taking a while.  The only thing I can think of is that somehow one
of the ICs on one of the relay cards is going bad, which sometimes
draws a bunch of current from the 5V rail coming from the DAQPad (and
the USB bus), thus causing the DAQPad to lose communication with that
USB bus.

FYI, I am running the 6508s off of the supplied external power supplies, not the USB bus.

Any more thoughts, please let me know.

Thanks,
Ryan