Vaidehi,
Are you using LabView 7.0 or newer (with DAQmx) or are you using an older version of LabView that only has the Traditional DAQ? Either way, there are several examples of analog waveform output included in LV. You can find them in the help menu under "Find Examples."
You coud get the AO config error for several different reasons. Its very hard to tell what it is without having the code. Are you doing simultaneous AI and AO? There is a shipping example for that also.
If you can't get this solved using the shipping examples please feel free to respond to this with your code attatched. It may give me some insight into whats going on.
-Sal