Several of the webpages in my asp.net web application have started returning a blank page after postback. Either it happens when clicking a button to run a procedure (save), or by selecting a value from a dropdown list. This is new behavior. The only change to code that has happened lately is implementing PKI. It does not happen all of the time but it happens often enough that users are really complaining. One avenue I thought of is sessions. I noticed on one page that if I work thorough it and submit, it seems to work. If I step away or do something else for just a few minutes, when I come back and make a change to the form like select something from the dropdown list, I get the blank page. I've asked this question here before but have not gotten any responses. I've also asked several developers I know but still no go. Any help is appreciated.