James,
Unfortunately this seem like a question to ask by phone, because we need a more extensive troubleshooting and understanding (www.ni.com/ask) as far as meantime suggestions you can re-check that in your Daqcard you have your channels set as Non referenced single ended (NRSE). Also check your cable and pin connections, a bad cable or pin may cause this kind of "out of normal noise levels". Farther than that with this information we cannot come up with something else, please give us a call to extend the troubleshooting for this.
Good Luck!...
Nestor Sanchez
Applications Engineer
National Instruments
Nestor