I have been having trouble with the Add Media options when creating posts or pages. I tried everything in the sticky, but none of it helped, so I dove into the code.
I was not having problems with the upload. My problem was with the "From URL" part of the form. Whatever I entered into it seemed to cause a blank screen to come up and nothing happened.
In wp-admin/includes/media.php, there is a function called media_send_to_editor. It looks like this:
function media_send_to_editor($html) {
?>
<script type="text/javascript">
<!--
top.send_to_editor('<?php echo addslashes($html); ?>');
top.tb_remove();
-->
</script>
<?php
exit;
}
I found that the addslashes function referenced was taking what a value for $html that looked like "<img src='http://wordpress.org/img.jpg'>" and turning it into "<img src=''http://wordpress.org/img.jpg''>". That was messing up the javascript.
So, I changed it too look like this:
function media_send_to_editor($html) {
?>
<script type="text/javascript">
<!--
top.send_to_editor('<?php echo $html; ?>');
top.tb_remove();
-->
</script>
<?php
exit;
}
Now it works fine.