The #N/A error isn't strictly an error like the other types displayed by Excel. It simply means the information the formula is looking for isn't available at this time. For example, if a formula was looking for the colour "blue" in the list:

green
yellow
orange
black
red

The result would be #N/A because "blue" is not in that list; however, the formula is still working perfectly.

Hope this helps.

Cheers,