Works for me, too, with daily build. Tested with virtualbox and a similar setup 
like evgeni. Did not use a label either. Although it would be cool to activate 
encryption support by just providing a label instead of a bootoption, IMO.
I had to boot a couple of times because I copied persistence.conf to the wrong 
place outside of the image ;) But that's why I realized that the error message 
appears only on the first boot! I have not found out yet why this is happening.