By visiting admin/modules, you cleared the cache without knowing it. There are several things in Drupal that clear the cache or portions of it (them), automatically.
No, clearing the cache is not risky. On a typical day of development, I probably do it at least a half dozen times. That's one of the great things about the Admin Menu (and one of the reasons I hate the core Toolbar). Any time something weird happens in Drupal, clearing the cache is the first thing to try. Just don't do it often on a live
site because it does have performance implications.
Nancy
From: celati laurent <lcelati@latitude-geosystems.com>
I wanted to thank everybody for your reply and your help. I
downloaded the new version of the administration module. Thank to
your help i succeed to activate the menu admin in tapping
/admin/modules.
The menu admin reappeared ;-) But I have not yet dared to clear
my cache. Is not risky?. You think I can really click on "clear
on cache"?