Somehow, a HTML newline tag appears in some (longer?) URLS, after parsing. See my post here
It looks like MsMittens' post above mine also has the same bug, but she encapsulates the url in a quote (?) Don't know what's up with that. Maybe it's the string http://secunia.com/multiple_browsers...rability_test/ that gets broken off because it's to long?
I disabled the "Automatically parse URLs" option in this post.
There also appears a space in the URL (right after the slash between 'secunia.com' and 'multiple_browsers'. This happening in an ordinary word in a post is OK (it forces wrapping of long words) but it shouldn't happen in parsed URLs.