I've googled but I haven't been able to find someone with a similar problem. I am getting this error in eclipse on several of my own projects as well as eclipse jars like this one. My project won't compile because of these issues.
!ENTRY org.eclipse.core.resources 4 2 2012-09-04 17:17:18.695 !MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.core.resources". !STACK 0 java.lang.SecurityException: Invalid signature file digest for Manifest main attributes at sun.security.util.SignatureFileVerifier.processImpl(SignatureFileVerifier.java:240) at sun.security.util.SignatureFileVerifier.process(SignatureFileVerifier.java:193) at java.util.jar.JarVerifier.processEntry(JarVerifier.java:305) at java.util.jar.JarVerifier.update(JarVerifier.java:216) at java.util.jar.JarFile.initializeVerifier(JarFile.java:341) at java.util.jar.JarFile.getInputStream(JarFile.java:406) at org.eclipse.pde.internal.core.ExternalLibraryCache.extractJar(ExternalModelManager.java:320) at org.eclipse.pde.internal.core.ExternalLibraryCache.getExtractedLibraries(ExternalModelManager.java:234) at org.eclipse.pde.internal.core.ExternalModelManager.getExtractedLibraries(ExternalModelManager.java:160) at org.eclipse.pde.internal.core.PDEClasspathContainer.addExternalPlugin(PDEClasspathContainer.java:72) at org.eclipse.pde.internal.core.RequiredPluginsClasspathContainer.addPlugin(RequiredPluginsClasspathContainer.java:256) at org.eclipse.pde.internal.core.RequiredPluginsClasspathContainer.addDependency(RequiredPluginsClasspathContainer.java:230) at org.eclipse.pde.internal.core.RequiredPluginsClasspathContainer.addDependency(RequiredPluginsClasspathContainer.java:214) at org.eclipse.pde.internal.core.RequiredPluginsClasspathContainer.computePluginEntries(RequiredPluginsClasspathContainer.java:129) at org.eclipse.pde.internal.core.RequiredPluginsClasspathContainer.getClasspathEntries(RequiredPluginsClasspathContainer.java:88) at org.eclipse.jdt.internal.core.JavaProject.resolveClasspath(JavaProject.java:2695) at org.eclipse.jdt.internal.core.JavaProject.resolveClasspath(JavaProject.java:2853) at org.eclipse.jdt.internal.core.JavaProject.getResolvedClasspath(JavaProject.java:1958) at org.eclipse.jdt.internal.core.JavaProject.computeExpandedClasspath(JavaProject.java:506) at org.eclipse.jdt.internal.core.JavaProject.computeExpandedClasspath(JavaProject.java:528) at org.eclipse.jdt.internal.core.JavaProject.getExpandedClasspath(JavaProject.java:1563) at org.eclipse.jdt.internal.core.builder.NameEnvironment.computeClasspathLocations(NameEnvironment.java:93) at org.eclipse.jdt.internal.core.builder.NameEnvironment.(NameEnvironment.java:41) at org.eclipse.jdt.internal.core.builder.JavaBuilder.initializeBuilder(JavaBuilder.java:603) at org.eclipse.jdt.internal.core.builder.JavaBuilder.build(JavaBuilder.java:167) at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:728) 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:239) at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:292) at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:295) at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:351) at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:374) at org.eclipse.core.internal.resources.Workspace.buildInternal(Workspace.java:513) at org.eclipse.core.internal.resources.Workspace.build(Workspace.java:422) at org.eclipse.jdt.internal.ui.util.CoreUtility$BuildJob.run(CoreUtility.java:165) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
The webernets tells me that there's an issue with a specific jar file, but I've not encountered explanation that has this issue on several jar files. I am using Helios service pack 2 and I'm using the same zip (for Helios) on another machine (and don't get these errors) so I don't think the issue is a corrupt file in the download.
