Did you find the solution to your problem? We are having a similar problem.
Only SSL is failing. One of our customers is using BC to post to our site and it gives him a “untrusted certificate” exception. But when they post the same values through a browser to the same service, they are able to post the values succesfully and there is no problem.
The customer says that they are able to use SSL and post to another vendor succesfully.
Any suggestions? Currently, they do not have any certificate on their end.