Thanks - I appreciate your advice. I've done more research and found that the error never occurs with a direct connection. It seems the application is expecting something that isn't being passed along via the proxy. The backend IIS reports that an "object reference is not set to an instance of an object." I'm not sure how to solve this, but retrying the connection probably isn't the best solution to my issue.
Thanks again for your help.
Thanks again for your help.