BP 1.2.3: Sitewide Activity RSS Feed

Hello,

We have Buddypress 1.2.3 installed on WPMU 2.9.2, and the RSS feed for our Sitewide Activity is not working properly. We receive the following error message:

XML Parsing Error: XML or text declaration not at start of entity
Location: http://www.generation-europe.eu/summit2010/activity/feed/
Line Number 2, Column 1:<?xml version="1.0" encoding="UTF-8"?>
^

After searching different WP support forums, I found a potential solution: adding the following lines of code to the PHP file that generates the RSS feed:
$out = ob_get_contents();
$out = str_replace(array("\n", "\r", "\t", " "), "", $input);
ob_end_clean();

I added these lines to the file /buddypress/bp-activity/feeds/bp-activity-sitewide-feed.php, but that seems to break the RSS feed entirely (blank page, not even an error message). I did notice the BuddyPress PHP feed files do not have the "$more = 1;" line as do the regular WordPress PHP feed files. Don't know if that's part of the problem...

Any ideas what I should try next?

Thanks!