Estou recebendo repetidamente erros ao criar o apk. Fizeram as coisas básicas, como limpar, atualizar e reiniciar o eclipse, mas ainda não está sendo resolvido. Aqui está o log de erros.

com.android.dx.util.DexException: Multiple dex files define Lcom/nineoldandroids/animation/Animator$AnimatorListener;
    at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:592)
    at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:550)
    at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:531)
    at com.android.dx.merge.DexMerger.mergeDexBuffers(DexMerger.java:168)
    at com.android.dx.merge.DexMerger.merge(DexMerger.java:186)
    at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:300)
    at com.android.dx.command.dexer.Main.run(Main.java:232)
    at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at com.android.ide.eclipse.adt.internal.build.DexWrapper.run(DexWrapper.java:187)
    at com.android.ide.eclipse.adt.internal.build.BuildHelper.executeDx(BuildHelper.java:813)
    at com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.build(PostCompilerBuilder.java:597)
    at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:726)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:199)
    at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:321)
    at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:396)
    at org.eclipse.core.internal.resources.Project$1.run(Project.java:618)
    at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2344)
    at org.eclipse.core.internal.resources.Project.internalBuild(Project.java:597)
    at org.eclipse.core.internal.resources.Project.build(Project.java:124)
    at com.android.ide.eclipse.adt.internal.project.ProjectHelper.doFullIncrementalDebugBuild(ProjectHelper.java:1116)
    at com.android.ide.eclipse.adt.internal.launch.LaunchConfigDelegate.launch(LaunchConfigDelegate.java:147)
    at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:855)
    at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:704)
    at org.eclipse.debug.internal.ui.DebugUIPlugin.buildAndLaunch(DebugUIPlugin.java:1047)
    at org.eclipse.debug.internal.ui.DebugUIPlugin$8.run(DebugUIPlugin.java:1251)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)