We recently upgraded a machine from Windows 2000 to Windows XP Pro (Sp2). Now, Windows explorer, if the machine is left to run for 2 or so days, will not refresh. This is to say that if you delete a folder in explorer, it doesn't leave until you hit F5 (or Refresh). If you click New | Folder, it doesn't do anything until you hit refresh and a folder named "New Folder" appears. A reboot appears to clear up the issue temporarily.
Any idea what could be causing this?