Advanced Guestbook 2.3.1 Password problem.

When I log into Admin on the Advanced guestbook 2.3.1 I am taken into the admin page after I enter my USerbname and Password, when I click on any of the links to change or delete a comment I am asked to enter my Username and Password again, this takes me back to the main admin page, a continuous loop. Does anyone know why this is happening and how to rectify this so it does not happen again?

Any help appreciated.