When I empty the junk mail folder and it's quite full I right-click and "empty junk mail folder". Then folder will empty and then I get an error msg box that says, "Permission denied to get property unnamedclass filename" and the screen "fogs over" and I have to refresh to navigate the page again. It's happened many times now. M2 on FC3, using FF1.5 from different box.
Edit: It just happened emptying my Trash folder too.