HI Cat,
The self-test is one very fundamental function of the device. If it fails persistently, that usually indicates the device will need to be repaired. You can call into RMA at 866-275-6964.
Just out of curiosity, how long have you had the device? Have you ever had the device RMA'd before and if so, when? If you can provide a Serial Number, I could look this information up to answer my questions.
-Andrew
National Instruments