Hi Walter,
If the user is logged in, and you've just added the "must be logged in" requirement, then I don't see that there should be any difference in what happens. Any chance you can send me an example of the effect? I'm guessing something else is in play here, but I'm not sure what.
Maybe the "Must be logged in" is a red herring - try turning that off and see if the error goes away. If not then we need to look for the source of the error, regardless of the logged in status.
cheers
Bruce