For the past week or so, my ASP.NET app suddenly logs off users. The symptom is: a page takes a very long time to load, then they are prompted for their username password again (using ASP Membership). I made NO changes to my site whatsoever before this started happening. I have spent DAYS trying to track this down and the best I can come up with is a semi-known problem with IIS that apparently can be resolved by restarting IIS.
What would I need to tell support in order for this to happen? I know I should submit a support call, but I don't know what to ask for so that we don't go around in circles for a week.