I was following through the tutorial and got the following error when I attempted to check in a changed document in the workflow/rules example;
Unable to check in Content Node due to system error: The transaction was not committed - Can not perform operation since the node (id:91e66fc0-2c68-11da-98c3-2382aa2569cd) is locked by another user.
We've seen reports of this from a couple of people, but haven't been able to identify the cause. The most likely situation is a combination of CIFS being used with guest access and rules.
We don't see it in our internal builds, so when we make the next release soon, I would expect the problem to be resolved.