Its in my common.css - but I can see its the very last item in that file, so I may have added it! I've made so many customizations that I'm afraid I've lost track. It is in the original product results html though.
Also - you may try playing with the min-height to see the results.
Sorry to take so long getting back to you - you've probably figured this stuff out already.
I'm still tinkering with a number of items on our site - its never-ending. (www.intlarrivals.com) You can probably pull the style sheets, if you think it would help.