Hello Jorge,
Could you post what hardware you are using? The answer to that question is very dependent on how to attack the problem. Also, I have Traditional (Legacy) NI-DAQ and NI-DAQmx support for LabVIEW 7.1 on my system and don't have a "DSA excitation control.vi". Is this a custom VI that you wrote? If so, what sub-VIs are causing the problem?
-Alan A.