The file 'a-file-that-doesnt-exist.tpl' was looked for in the currently active skin and could not be located. In this case the skin was jrNingja, so the location searched at was:
/skins/jrNingja/a-file-that-doesnt-exist.tpl
There was no file there, so it could not be displayed.
The options are:
* put the file there.
* change the include call to include a file that IS there.