I’m getting the same type of error. I just installed the latest version of WordPress MU (1.2.1). I was not getting this error with the previous version. I noticed other threads where folks were having the same problem:
http://mu.wordpress.org/forums/topic.php?id=1514&replies=22.
I also noticed that there has been an open ticket on this issue:
http://trac.mu.wordpress.org/ticket/184.
The problem is marked as resolved. The fix has been applied to the latest version that I downloaded, yet I’m still experiencing the problem. Any other ideas as to what may be causing this?
I had a similar problem with my rss feeds. Basically, the permalinks to the RSS feeds would work as expected in IE, but not in Thunderbird or the Google reader. I kept getting an “invalid rss feed” error message from Thunderbird, and Google kept telling me that the feed was empty. I found that disabling Angsuman’s Authenticated WordPress Plugin fixed the issue. I don’t think it has anything to do with extra whitespace. I am not an expert in PHP, mod-rewrite, etc, but I suspect the problem has to do with the way that this particular plugin is redirecting the links.
