I also have a Microsoft Wireless Laser Desktop 5000, and I am having the same issue.
I found something interesting as I was using xev to see if the key events were happening. In Hardy, all the multimedia keys worked except for the 5 "My Favorites" keys in the center of the keyboard; these keys did not trigger an event in xev when pressed. Now the problem is opposite - the 5 My Favorites keys work, but _not_ the others.
I also have a Microsoft Wireless Laser Desktop 5000, and I am having the same issue.
I found something interesting as I was using xev to see if the key events were happening. In Hardy, all the multimedia keys worked except for the 5 "My Favorites" keys in the center of the keyboard; these keys did not trigger an event in xev when pressed. Now the problem is opposite - the 5 My Favorites keys work, but _not_ the others.