What load do you have connected to your channel(s) and what are you using to measure the current? What driver and version are you using (Traditional NI-DAQ, NI-DAQmx)?
It sounds like there could be a problem with your hardware or your driver installation. To troubleshoot the problem you could try uninstalling and reinstalling your driver, making sure you have the latest version to see if this makes a difference. You could also try the board in a different computer.
This type of issue can be difficult to resolve through the forums. If these suggestions do not help, I recommend that you request phone support at ni.com/support.