1. Upgrade to the latest SGOS 5.4 and 5.5 GA. At the time of writing, they are SGOS 220.127.116.11 and SGOS 18.104.22.168 respectively. If you are using BCAAA, it should be upgraded along to the version that comes with the new SGOS.
2. As a workaround, disable SSL protocol detection with the Content Policy Language (CPL) below :
url.host=av-download.bluecoat.com http.method=CONNECT detect_protocol.ssl(no)