I am trying this again. I have a ASP.Net web application that is returning a blank page on postback. The forms work for a minute when you open them. So if you fill out the form and hit submit fast enough, it seems to work. My tests will let the postback work as expected so long as the actions are done in 1 minute or less. One you get past 1 minute and click the submit/save button, or make a change in the drop down list, you get the blank page. I was thinking of session timeouts, but I have that all set to 60 minutes, both in web.config and IIS (its IIS6). The only change done recently is implementing PKI 2 weeks ago, and that is when this behavior began. I've asked this question all over, including here, but I have not found a solution yet. Any ideas would be greatly appreciated.