false positive blocked site

I've set it up so that basically all categories are blocked for each of our kids' accounts.  Then I unblock specific sites one at a time.  This has worked well until recently.  A site that was specifically listed in as "allowed" suddenly is being blocked when my child attempts to access it (this was not the case in the past for this site).  I've verified that it still appears in the allowed list.  The site is www.live365.com (a streaming site for internet radio).  The site is in the entertainment category, which I've blocked.  But I've set up the site itself as allowed.  Has something changed in your setup that makes this apparent mismatch happen?