After the plugin installation (v2.0 or v2.5) not displaying properly on my site: icons are displayed instead of page/fan images. I checked on the server, there were the pictures, but the size was 0 bytes. In the php_error.log I got this error message:
PHP Warning: file_get_contents() [function.file-get-contents]: URL file-access is disabled in the server configuration in …/plugins/facebook-fan-box-cache/facebook-fan-box-cache.php on line 330
For security reasons some servers set the allow_url_fopen PHP directive to off, therefore the file_get_contents not work.
The solution is to use the PHP Curl library to do so instead, which is more secure. I rewrote the lines (330 and 368 in v2.5) and the plugin is working.