Ok, I thought I had this solved with an earlier question, but we are still experiencing it. I recently implemented PKI with my ASP.Net web application (C# code behind), within the past week. Since then, I get users continually telling me that when they go to save something, they get back a blank page. This appears to be happening on PostBacks. It does not happen every time, but it does happen often and continually. Before enabling PKI, this never happened. This app has been running smooth for over 2 years. It always happens on a postback, when the user clicks save or selects something from a dropdown list. Any ideas what is happening? I've experienced it many times, too.