Heh I jus thad this problem. For some reason when I start a new NG project it keeps erasing the include file! Make sure to keep a backup file fo the include because this happens often. The most solid way to get an error free project Ive found it to load the 3rd person example.
Delete the code and then start your own code there. This usually starts a good solid program that will stop eating the include file.
If the include file is empty then its been erased and has to be put back! Also anyproject you make in a different folder be sure to include the dll. Took me 2 hours last night to get my project working with out eating the file. Once you get it stable its fine though. Im not sure why its so hard maby one of the NG creators could address this or give an explanation.
Its very hard to get a project started even the most basic of ones. It always eats the include file at first!
http://badtempergames.tripod.com