Pretty sure Jochen put something in the readme about this, you have to register the OCA as an administrator in Vista.

Find the shortcut to a command prompt (All Programs -> Accessories) and RIGHT click. Select "Run as Administrator", the enter the administrator password or accept the action in the resulting dialog. Change directory to the folder where you installed NavCoder eg :

CD \Downloads\NavCoder

then run the command :

regsvr32 comdlg32.ocx

This should register the OCX control and allow you to run NavCoder.