Same issue for me using 5.5 . Just updated to Mavericks without doing any research and Encore crashes as soon as I try to do anything with it. As a wedding videographer its a massive problem. Thankfully weddings have finished for the year so I have a bit more time to try and resolve things. The way I see it at the moment, I could update to cs6 to see if that works, or buy Mountain lion from App store and go to that and hope for the best. In the meantime I have just burned a blu-ray in Toast Titanium as a trial. It works but took a long time and the menu options are pretty poor.
Would love to hear if anyone is running cs6 encore with Mavericks with no problems.