I found the solution to my problem by trying different command-line inputs found within this thread: http://forum.pfsense.org/index.php/topic,18948.0.html

Incidentally, I changed the SSH listening port from 22 to another in the 8xxx range as an experiment. Oddly enough, I'm still seeing 50 blocked SSH login attempts an hour via denyhosts. How can that be?

Anyway...here's an excellent article from 2006 about the security issues associated with using SSH. I suggest everyone go through it and use the information contained within to re-evaluate whether their SSH is buttoned down tightly.

http://www.securityfocus.com/infocus/1876