With Eclipse Galileo you go to Eclipse -> Preferences menu item, then select Java and Compiler in the dialog.
Now it still may show compiler compliance level at 1.6, yet you still see this problem. So now select the link "Configure Project Specific Settings..." and in there you'll see the project is set to 1.5, now change this to 1.6. You'll need to do this for all affected projects.
This byzantine menu / dialog interface is typical of Eclipse's poor UI design.