Using Preview instead of Acrobat

Is there any way to make Firebird open PDF files with preview instead
of Acrobat?  Preview is already my system default, but Firebird
doesn't respect this.  If I go into the download preferences and try
to select a different app, Preview is grayed out and not selectable. 
There is no option to show all apps, like in most dialogue boxes.  If
I delete the PDF entry from download preferences Firebird will prompt
me to pick an application the next time I try to looad a PDF file, but
Acrobat is the only option to choose from.

Any advice? I can't think of anywhere else to look.