Files on Desktop not updating

view story

http://askubuntu.com – I noticed that when I would, for example, download a file to my Desktop, it would not be reflected visually. That is, I did not see any icon for the file. Curious, I checked in terminal (ls) and the file was there. I had managed to solve this by killing nautilus (killall nautilus) then restarting it (nautilus &). So I'm wondering: why did Nautilus no longer update? Is this a known bug? Is there a config file I need to tweak? (HowTos)