I modified the code in the example 'messages' bundled with Seam.
I injected a (session) UserAccount to the class MessageManagerBean and modified the findMessages to include a where clause in the query. It worked like a champ and all corresponding messages belong to this user were found and displayed correctly.
However when I clicked on any of the messages, I got an injection error:
SEVERE: org.jboss.seam.RequiredException: In attribute requires non-null value: messageManager.userAccount
This userAccount was injected correctly for the findMessages to work. So why couldn't Seam find it now?