I was getting the 15003 error last week. Turned about to be a problem with the cloud. May want to review the KB article listed in this tread to failed open for that error.
I've heared there was a TrustedSource library update this morning, and the switch from the old one to the new lib could cause problems with HTTPS communication. This can also affect HTML Authentication.
Please restart MWG. This should solve the problem.
I believe the update was the problem. See KB https://kc.mcafee.com/corporate/index?elq_mid=5166&elq_cid=2540563&page=content& id=KB71102
I put the settings back that I had for SSL Scanner to skip Finance / Banking sites and it has been working fine.