Eclipse "this compilation unit is not on the build path of a java project"

I can't get autocompletion to work in Eclipse.

I'm working on the project on svn. I set up the project in Eclipse by going into

File -> Import -> Checkout As a Project -> New Project Wizard.

I chose Enterprise Java Application. Everything seemed to work fine except instead of autocompletion working as I expected I got a popup dialog displaying the message

This compilation unit is not on the build path of a java project.

I've Googled it and everyone says that the project must be a Java project, but it is! What is the problem?

Update

The catalog structure on svn looks like this:

-Project_name
  -application
     -META-INF
       application.xml
       MANIFEST.MF
  +build
  +db
  +deploy
  +dist
  +lib
  +properties
  +script
  -src
     -META-INF
        someother.xml (datasource info)
        persistence.xml
        folder hierarchy with source files (should be package)
  -web
     some folders
          .
          .
     files
       .
       .
     -WEB-INF
        faces-config.xml
        jboss-web.xml
        web.xml
     build_win.xml

How do I tell Eclipse where the source files folder, application.xml, and other configuration xml files are?