I had an issue where a client uploaded files which had spaces in the file name and the getimagesize failed because of this. The manual on php.net outlines paths must be escaped properly before passing to getimagesize, http://php.net/manual/en/function.getimagesize.php.

I'm using version 6.x.1.6

I put in this change in taxonomy_image.module on line 243
//$image[$tid]->url = file_create_url($mypath . urlencode($image[$tid]->path));
$image[$tid]->url = $fullpath . urldecode($image[$tid]->path);

and on line 262
//$image[$tid]->url = url($fullpath . $image[$tid]->path, array('absolute' => TRUE));
$image[$tid]->url = $fullpath . urldecode($image[$tid]->path);

Now it works properly for any properly filename uploaded and I removed the URL part as getimagesize is able to be pasted a path from the webroot of the site.