The red crossed circle has disappeared from the Junk Mail folder. I tried starting Outlook with the folder reset switch, but no luck. The icon is still the standard folder icon.

As long as the Empty folder commands work, it's not broken, but to restore the junk folder icon, you'll need to make a new data file.

If you use Exchange server, login to your account using OWA and verify the icon is on the junk mail folder in your mailbox. If it is (in all cases so far, it has been OK in OWA), close Outlook and delete the offline data file (*.ost). In Windows 7, its at %localappdata%\microsoft\outlook (paste that into the address bar of Windows Explorer and press Enter.)

Using the Resetfolders switch

Open outlook with the /resetfolders switch:

Close Outlook. At the Start search field on Vista or Windows7 Start menu or in the Start menu, Run command (Windows key + R), type

outlook.exe /resetfolders

Then press Enter (or OK button) to restart Outlook.

Note: Make sure there is a space between the words.