Eu estou tentando usar o r.js para otimizar meu código, mas continuo correndo para este erro:

Dependências de rastreamento para: init

Error: Load timeout for modules: backbone,jquerymobile

O comando que estou executando é o seguinte:

$ java -classpath /Users/dixond/build-tools/rhino1_7R4/js.jar:/Users/dixond/build-tools/closurecompiler/compiler.jar org.mozilla.javascript.tools.shell.Main /Users/dixond/build-tools/r.js/dist/r.js -o /Users/dixond/Sites/omm_mobile/js/build.js

Meu arquivo build.js é assim:

( {
    //appDir: "some/path/",
    baseUrl : ".",
    mainConfigFile : 'init.js',
    paths : {
        jquery : 'libs/jquery-1.8.3.min',
        backbone : 'libs/backbone.0.9.9',
        underscore : 'libs/underscore-1.4.3',
        json2 : 'libs/json2',
        jquerymobile : 'libs/jquery.mobile-1.2.0.min'
    },
    packages : [],
    shim : {
        jquery : {
            exports : 'jQuery'
        },
        jquerymobile : {
            deps : ['jquery'],
            exports : 'jQuery.mobile'
        },
        underscore : {
            exports : '_'
        },
        backbone : {
            deps : ['jquerymobile', 'jquery', 'underscore'],
            exports : 'Backbone'
        }
    },
    keepBuildDir : true,
    locale : "en-us",
    optimize : "closure",
    skipDirOptimize : false,
    generateSourceMaps : false,
    normalizeDirDefines : "skip",
    uglify : {
        toplevel : true,
        ascii_only : true,
        beautify : true,
        max_line_length : 1000,
        defines : {
            DEBUG : ['name', 'false']
        },


        no_mangle : true
    },
    uglify2 : {},
    closure : {
        CompilerOptions : {},
        CompilationLevel : 'SIMPLE_OPTIMIZATIONS',
        loggingLevel : 'WARNING'
    },
    cssImportIgnore : null,
    inlineText : true,
    useStrict : false,
    pragmas : {
        fooExclude : true
    },
    pragmasOnSave : {
        //Just an example
        excludeCoffeeScript : true
    },
    has : {
        'function-bind' : true,
        'string-trim' : false
    },
    hasOnSave : {
        'function-bind' : true,
        'string-trim' : false
    },
    //namespace: 'foo',
    skipPragmas : false,
    skipModuleInsertion : false,
    optimizeAllPluginResources : false,
    findNestedDependencies : false,
    removeCombined : false,
    name : "init",
    out : "main-built.js",
    wrap : {
        start : "(function() {",
        end : "}());"
    },
    preserveLicenseComments : true,
    logLevel : 0,
    cjsTranslate : true,
    useSourceUrl : true
})

E meu init.js é assim:

 requirejs.config({
      //libraries
      paths: {
          jquery:       'libs/jquery-1.8.3.min',
          backbone:     'libs/backbone.0.9.9',
          underscore:   'libs/underscore-1.4.3',
          json2 :       'libs/json2',
          jquerymobile: 'libs/jquery.mobile-1.2.0.min'
      },

      //shimming enables loading non-AMD modules
      //define dependencies and an export object
      shim: {
          jquerymobile: {
              deps: ['jquery'],
              exports: 'jQuery.mobile'
          },
          underscore: {
              exports: '_'
          },
          backbone: {
              deps: ['jquerymobile', 'jquery', 'underscore', 'json2'],
              exports: 'Backbone'
          }
      }
    });


requirejs(["backbone",], function(Backbone) {
    //Execute code here
});

O que estou fazendo de errado nesse processo de criação?