I'm working on a site here , and last night about 8:00, the menu would only display the pages under the default page.  In addition to that, none of the links would work by either page clicks or  direct reference (from bookmarks).  I know it's not the menu module because I've seen this behavior once before in testing with another module.  One of our techs recycled the worker processes in the application pool and this seemed to fix the problem, but I have NO idea how this happened in the first place.  When I first created the site, there was some strange behavior when I was creating pages and copying panes by reference where sometimes modules would dissapear until I restarted dnn, but aside from that I don't have much else to go on. 

Can anyone offer any suggestions as to what might be happening?