Error in class-IXR.php

I appologize if this has been discussed before, but I could not find any reference to it…

I have just upgraded to version 2.0.1 and everything seems to be working perfectly except for one small problem. When I attempt to post an entry, or save an edited entry, I get the following error:

Warning: Cannot modify header information – headers already sent by (output started at /var/www/html/blog/wp-includes/class-IXR.php:497) in /var/www/html/blog/wp-admin/post.php on line 122

I have taken a look at line 497 in class-IXR.php and the actual line, and function call is exactly the same in 2.0.1 as it was in the previous version.

This is the section that is apparently having the problem in function query():

if ($this->debug) {
echo ‘<pre>’.htmlspecialchars($request).”\n</pre>\n\n”;
}

.. which makes me think that I am somehow in debug mode, but I don’t recall setting it?

I am tempted to just replace the new class-IXR.php with my old one, but am not sure how that will effect the rest of the blog. Or if it will even matter since the function call appears to be the same.

As I said, everthing else appears to work fine. The posts even actually get posted, but I am left with a page of XML data and an error instead of being returned to the admin page.

Anyone else seen anything like this?