Right Click On Taskbar Does Not Work

On my personal computer, I noticed the Quick Launch on the taskbar had “disappeared”. When attempting to replace it by right-clicking on the taskbar (to unlock), nothing happened. I am able to right click on the desktop, the start menu…anywhere else but any blank area on the taskbar.
Also – when right-clicking on the desktop, properties and then to “Display”, I can no longer change the wallpaper through that method.
(Windows 2000 Professional)
Any helpful suggestions are greatly appreciated.