I just read the following thread http://forum.pfsense.org/index.php/topic,25795.0.html.
It also points to http://doc.pfsense.org/index.php/Logs_show_%22blocked%22_for_traffic_from_a_legitimate_connection,_why%3F, which states that "It is harmless, and does not indicate an actual blocked connection".
However, users are still reporting problems connecting to a web site or to a mail server (on port 443).
Anything else that can be done?