I know there have been many of you who are part of the Flash Builder pre-release program and have tried to use LCDS builds from labs. There have been changes in FB and LCDS that will prevent this from working. You will need the LCDS pre-release builds. If you are already a member of the Adobe pre-release program use this link : https://prerelease.adobe.com/callout/default.html?callid=7A951966ECA340E4A6BA309 ACE90BA46
to join LCDS pre-release.
If you are not a member of the pre-release program, fill out this application (https://www.adobe.com/cfusion/mmform/index.cfm?name=prerelease_interest) to join the pre-release program