The error message you are getting:
Warning: move_uploaded_file(/home/comite/public_html/admin/prensa/../../images/prensa/lg/fb6a7b6c31a5f146491c3253e9ddc19e_tmp.png) [function.move-uploaded-file]: failed to open stream: Permission denied
means that you do not have Write Permissions on the images/prensa/lg/ directory on the server.
check with your ghost to determine what tools they have available for managing directory permissions and make sure to give write access for all users to the folders you wish to upload images to.