Users of Apache Flex SDK 4.10.0 (and future releases until this issue is addressed) will experience a bug in Adobe Flash Builder 4.7 and Adobe Flash Builder 4.6) when creating a new project that uses Spark Application. Flash Builder will incorrectly insert the following attribute in the Application tag:
This will result in a compile error in the new project. The remedy is to simply remove the errant attribute.
Members of the Adobe Flash Builder team are aware of the problem and investigating ways of correcting the problem in Flash Builder 4.7. It is unlikely that Adobe will address the problem in Flash Builder 4.6 because only Flash Builder 4.7 officially supports Apache Flex SDKs.
This page will be updated to reflect the latest information we can get from the Flash Builder team regarding this issue.
Update: September 4, 2013
Adobe has made a patched .jar available here: http://helpx.adobe.com/flash-builder/kb/flex-new-project-issue--.html