Following the upgrade to Drupal 6, I noticed an awkward error when publishing content from my desktop editor (Ecto 3). From what I've read, it will affect any editor that uploads content via the blog api integrated in Drupal 6.
How to resolve:
It looks like it's down to the version of libxml2 and php involved. You can either:
I went with option 2 and it's not as scary as it sounds.