Sudo asking again

[Peter Plessas <plessas@mur.at>]

Dear List,

i have discovered something strange and would appreciate any advice:

as i use sudo as ordinary (and only user) on my system, having happily 
used it for two years now, it asks me for a password again. You are 
perhaps familiar with the dialog:

>We trust you have received the usual lecture from the local System
>Administrator. It usually boils down to these three things:
>
>    #1) Respect the privacy of others.
>    #2) Think before you type.
>    #3) With great power comes great responsibility.

The only change i made to the system was setting the hardware clock's 
date (by accident) one day backwards.

As i am a little bit suspicious about entering passwords without an 
apparent reason, i would like to know if this behavior has occurred to 
someone else.

regards,

Peter

PS: please reply directly as well, as i am only in digest-mode for now.