404 everywhere

I was just playing around with a fresh install of drupal.
Looking at the administrative interface to get an idea of what I could
do.

Then I decided to start to edit somthing starting from the motto.

Suddently I started to get 404 on every link. I can just reach the
homepage of the administrative interface (http://mysite/drupal/).
Nothing else.

The only relevant thing I saw that could produce such a devastating
effect in what I was playing with was the "clean url" switch.

Any other hint? How could I solve this problem?

I'm not the sysadmin so I don't have a clue about the version, but it
was installed from source on a Slackware in mid of June.

thx

-- 
[ Drupal support list | http://list.drupal.org/ ]