trackbacks problem

I found one post, but no replies to a similar ‘trackback’ problem I’m having with one of my student’s blogs.
Can anyone point me to a help section / answer, please?
The trackbacks on their blog is not functioning.
One user received this error message:
1.Just a note, your trackback seems broken. Something about “Cannot redeclare class streamreader in ./wp-includes/streams.php on line 26″
Any ideas and suggestions will be greatly appreciated. Thanks.
This post http://wordpress.org/support/3/9632 is similar.