HEHEHEHEHEEEE
ur sure ur using a NON - PIRATED version, cos mostly these problemos occur on Pirated versions. If not and uv paid for it, "Symantec Customer Support" should be the place u head too.
Alternately, try uninstalling NAV followed by a fresh installation, here in the installation phase, when it asks u for the 4 Post Installation Tasks, UNCHECK all of them......Just check it out, Post INSTALL, they WILL be checked....