in a custpack there should be at least

Customize.xml
preloaded_config.xml
CONTENT_DOWNLOAD_HOOK.itm
FM_PICTURES_HOOK_3.itm
FM_SOUNDS_HOOK_3.itm
FM_THEMES_HOOK_3.itm
FM_VIDEOS_HOOK_3.itm

double check your uploading the files correctly and in the right place, if it still doesn't work then try xs++3.1