Hi
Lots could be wrong here,
Your best bet is to open up the NAV Classic client, click on "Help"->"C/SIDE reference Guide"
Click "Index" and type the following into the search box
Web services, about
This will run you through everything you should do to setup the NAV side of things and get the web service running
Let me know if you still have issues after these setups
Cheers
Nev