Generate Post Thumbnails plugin was improved (http://wordpress.org/extend/plugins/generate-post-thumbnails/) and now it supports different methods of uploading externally hosted images on server depending on server configuration. Some configurations (allow_url_fopen is Off) didn’t work before and created empty images. This version should fix this. Also it supports relative paths.
Plugin home page:
http://wordpress.shaldybina.com/plugins/generate-post-thumbnails/
Related posts:
Tags: fixes, plugin, thumbnails, updates