Thanks for the report! This is strange. I'm wondering if there's some permissions issue with your /opt directory. Do you get the same behavior if you just unzip and run from your home dir?
!ENTRY com.google.dart.tools.core 4 0 2012-08-08 19:19:14.083
!MESSAGE /opt/dart-editor/dart-sdk/bin/dart was not executable
!ENTRY org.eclipse.ui.workbench 4 2 2012-08-08 19:19:14.213
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.ui.workbench".
!STACK 0
com.google.dart.compiler.InternalCompilerException: Failed to open /opt/dart-editor/dart-sdk/lib/config/import_any.config