All the while I thought that the AppDomain only restarts when the web.config, global.asax, bin folder (or it’s contents) is changed and if there are considerable number of files have changed (15 is the magic number as they say but can’t verify).

All the while I was wrong, by default (that is without tweaks), deleting a folder under your application will restart the AppDomain (implies but not limited to clearing all sessions, cache etc).

Took me a considerable time to trace the issue I have more than guesses on what’s messing the application. http://weblogs.asp.net/owscott/archive/2006/02/21/ASP.NET-v2.0-_2D00_-AppDomain-recycles_2C00_-more-common-than-before.aspx http://objectsharp.com/cs/blogs/bruce/archive/2004/11/01/992.aspx http://blogs.msdn.com/toddca/archive/2005/12/01/499144.aspx

And thanks to Performance Monitor (Start > Run > perfmon or Adminstrative Tools > Performance) for the hints that there is something messing with my sessions and cache.