Can't remove app icons from the desktop

I installed AdwLauncher. In the beginning it worked well. But now, I can't delete the app icons from the desktop. The situation is that when I longpress the desktop, the list doesn't show up so that I can't add shortcuts, apps or widget to the desktop. Also, when I longpress the app icon on the desktop, list doesn't show up so that I can't remove, delete or edit the icon. My cellular is HTC Desire. Is this a bug problem or I just set up in a wrong way? Restarting the phone didn't help. I used "home switch" to change the launcher back to HTC sense, then changed back to ADW but it still remains the same.