Kivinen has some great tools for working the the toolset on his site here:
http://www.kivinen.iki.fi/nwn/
One of the best tools for debuging your module is his check module tool, which can be downloaded here:
http://www.kivinen.iki.fi/nwn/exe/check-module.exe
You can find the documentation here:
http://www.kivinen.iki.fi/nwn/docs/check-module.html
Some have suggested you will actually need to save the module out to a directory.
After you find errors, you can try fixing them with his update-ifo tool:
http://www.kivinen.iki.fi/nwn/exe/update-ifo.exe
Here's the documentation:
http://www.kivinen.iki.fi/nwn/docs/update-ifo.html
He also has perl versions of everything, if you want more up to date options, but I've included the exe files since that's what most people will probably be grabbing.