Permissions getting reset inadvertently

Hi,

I just started using Drupal yesterday. I have built sites with joomla and have been running a mediawiki wiki for a while, so hopefully this isnt a completely stupid question. The site I am building is for the university department that I study in.

I have created a page called 'Faculty' and a role called 'faculty'. As the administrator, I have granted the role permission to edit the page. When I log in as my test faculty user I can view the page. I hit edit, make a tweak (i.e. pretending to a faculty member) and hit save. However, then the faculty member can no longer view the page. When I go in as the administrator I can see that the permissions on that page have been reset back to 'no access' (i.e. no checkboxes set). As the administrator I wanted to be able to grant permissions on certain pages to certain groups of users, but I do not want them to be able to change that permissioning. I hope this makes sense. My email address is me(at)andy-j-thornton.com if this does not make sense.

Cheers,
Andy