Outlook 2007, ZCO 6.05 - users are receiving e-mails and then adding e-mail addresses to their blocked sender list. Apparently the entries are being saved to the list correctly but the e-mails are not going to the junk folder as it is supposed to, they stay in the inbox.
I had a similar problem related to rules and it required a reg key - see here -
Rules not working
Not sure if there is a similar tweak for this one?