that's "normal" with multi WAN like you have. It's not a major issue, as everything will work as you desire, but I consider it a bug. I already have a ticket open on it.
http://cvstrac.pfsense.com/tktview?tn=1320,6
You can work around it by creating a rule permitting traffic to your OPT IP with no gateway selection, and move that rule to the top of your OPT ruleset.