In my new mac OSX 10.8.3, I install scala 2.10.0, play 2.1.0 and IntelliJ12, and create a play project as follows:
#install brew > ruby -e \"$(curl -fsSL http
This problems can be solved by generating the idea project with:
$ play # start play from command line [your-play-project] $ idea no-sbt-build-module
This will enable IntelliJ's default building mechanism for Scala, which won't cause these problems.