[SOLVED] Server error HTTP 500

Hi there,
I'm trying to duplicate the banner functionality in order to modify it according to my needs.
I've started by adding the menu item under System>Design (where banner is as well) and doing that I've just duplicated (and edited) all the occurrences of banner pages in the admin subfolders renaming them as shopwindows.xxx.

To be precise I've duplicated banner.xxx files under:
/admin/controller/design/
/admin/language/design/
/admin/model/design/
/admin/view/template/design/ (here you have banner_list and banner_form files)

then to add the menu item I've edited:
admin/controller/common/header.php
admin/language/english/common/header.php
admin/view/template/common/header.tpl
and set permission via System>Users>User Groups as explained in this topic.

Now I see the menu item in the admin menu under System>Design but when I click this server error http 500 is shown.
Any suggestions?
Thanks

Ok, I've found it. It was a misspelled method call!
Sorry.