I was trying to find out who triggered the failing Hudson build. But i found Started by an SCM change instead of Started by 'UserId'. Now, what does that mean?
It means that someone checked in code changes to your version control system / software configuration management (CVS, SVN, Git, etc), and Hudson started a built based on that change.
You should be able to see who it was by clicking the "Changes" link on the left menu.