Today I moved my wordpress.com blog to my own server (WordPress version 2.8.4). Of course, I wanted to ex- and import all my old articles, comments, images etc. Fortunatly, there is a special tool for that. Unfortunatly, this tool seems to be a kind of unstable. So I got the error
Remote file error: Remote file is incorrect size
But I found a little workaround for this.

In my case, the $headers['content-length'] doesn’t included the expected value. It contained the size of the file in an array instead of the raw integer. So my tiny workaround is to insert one line (in this example line 620) of code into the wp-admin/import/wordpress.php-file right after the declaration and the first occurence of $headers respectively. In the current stable release 2.8.4 it should look like this:

618 // fetch the remote url and write it to the placeholder file
619 $headers = wp_get_http($url, $upload['file']);
620 $headers['content-length'] = $headers['content-length'][1]; // insert this line right here


Note: The error message seems to be caused by several issues. So this solutions does not need to fit for your problem. Other workarounds can be found on the WordPress forum.