Rezn,
Aha, therein lies the problem. This was what I suspected, and thus my question as to which data acquisition card you are using. The DAQCard-AI-16XE-50 has analog inputs, digital I/O, but no analog outputs at all. So your card is working as it should, but it has no analog outputs.
If you have the 2002 National Instruments catalog, you can see this in a table on page 231 (your DAQ card is the one on the bottom), or check this pdf file:
http://www.ni.com/pdf/products/us/2mhw254-255e.pdf
Your card is also called the NI6012E. Check out the small table on the first page.
Mark