There’s a problem, on many servers, with the upload function(s) – it makes installing themes and plug-ins impossible from the administrative back-end. But, there’s a simple fix. Simply open the wp-config.php file and add the following code at the very bottom:

if(is_admin()) {
add_filter('filesystem_method', create_function('$a', 'return "direct";' ));
define( 'FS_CHMOD_DIR', 0751 );
}