This appears like the client PC is lacking Thawte root CA certificate. If this is true then you will certainly going to get these contents. Just seen for this in the Trusted Root CAs in pc store. If it is not included then it will be good for you if you can included this manually. I am sure that you will not obtain this content once again after including this. If you get any more trouble then please post back and we will test out to get this defeat in few other potential way.