Hello Chris,
The error is usually generated when the value is out of the range specified for the voltage output task. To my knowledge, there should be no scaling required before you output your data values. I would recommend trying two things.
1) Open up the following example and try running it after selecting the proper device/channel on the front panel.
C:\Program Files\National Instruments\LabVIEW 7.1\examples\DAQmx\Analog Out\Generate Voltage.llb\Cont Gen Voltage Wfm-Int Clk.vi
2) Open up Measurement and Automation Explorer and open a test panel for your DAQ board. Try seeing if you can successfully generate a +/-10V value.
Take care,
E.Lee
Eric
DE For Life!