theme storage directory

i've uploaded theme_editor.module to the modules directory, applied the patch to xtemplate.engine, and uploaded theme_editor_engine.engine to themes/engines/theme_editor. still, when i go to admin/theme_editor/configure to set the theme storage directory, it says "The theme storage directory does not exist or is not writable." this message still shows up no matter if i make a new directory or label it with permissions 666 or 777. help?? thanks