apt-watch ask for the root password

[Godfrey]

Dear ubuntu brothers and sisters,

Install apt-watch, add it panel.  After it finishs checking for
updates, the light bulb is on, then I double click it, It prompt by
saying "Running Synapic as root. Password:", so I key in the "old
friend" sudo password, then it's says "Authentication
failure". Meanwhile I use the vary same password when doing sudo.
Anybody have the same problem?