Maybe this will help someone, it's an exotic Outlook 2003 bug.
I make heavy use of Outlook's 'Views' to change how data is presented to me and I create my own custom views. This is particularly important for tasks. A couple of months ago Outlook stopped showing me the list of views -- I could only see a single view choice in the Advanced Toolbar Current View drop down list, or in the 'View:Arrange by:Current view" menu drop down. It always showed the current view. To change views I had to bring up the View edit menu and apply from there.
I thought this bug was related to our ancient corporate exchange server, but an upgrade to the latest version didn't fix it. It only happened with the Tasks stored on the exchange server, not archived tasks stored in my PST files.
The fix was, of course, to delete every custom view I ever created and reset every Outlook view to its defaults. Now the drop down works again. It's not that hard for me to recreate was was lost, so this is a big improvement.