Broken page error when going to the login page a private Drupal built site

I had an odd effect when I installed PDF creator tool bar on a windows 7 PC with both Firefox and MS Explorer. Opera still worked on this page and following  uninstalling the toolbar, both Firefox and MS Explorer were also ok once more.

This is a simple private site the first page has areas that can not be shown until the user logs in and it may be this that give the problem although I have not seen any problem with this page and none of the users have had access issues. If you would like to take a look for yourself go to to see the effect. It looks at if you are using Druple yourself so you may well have the answer to hand

Many regards