How to set up Joomla directory permissions in Joomla 1.5?
Set the following directories to 777 using an FTP client.

cache
components
images
language
media
modules
plugins
templates
tmp

administrator/backups
administrator/cache
administrator/components
administrator/language
administrator/modules
administrator/templates

administrator/language/en-GB

images/banners
images/stories

plugins/content
plugins/editors
plugins/editors-xtd
plugins/search
plugins/system
plugins/tmp

language/en-GB