TrustFailure: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel

I'm using .netCHARGE (http://www.dotnetcharge.com/) to process credit cards and I'm getting the error: "TrustFailure: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel." everytime I try to process a payment. I read through previous SO posts that match this error and have tried the SSL Diganostics Tool, but now I'm unsure what the problem could be.

.netCHARGE is just a dll in the /Bin directory, do I need to do something particular to this to allow it to use the site's SSL certi开发者_开发百科ficate?

Help appreciated. :)

For future reference to other SO users; this was caused by the receiving bank, not a problem with IIS, .netCHARGE or the code. The bank was refusing the traffic due to the account setup.