Plugin returns no results for different key values

Hi,
I successfully activated "Global Site Search" plugin on my WordPress installation, and it works.

There are, however, different key values that returns "Nothing found for search term(s).", but I'm pretty sure there are MANY results with these keys...

This is the search page:
http://ziogiorgio.com/site-search/

And these are some of the broken keys:
light, spotlight, event...

Any suggestions?

Thank you