Problem with content assistent

Check the error log, it may have useful information for telling what the problem is. Go to Window -> Show View -> Error Log. (or search it in Other... if it doesn't immediately appear).

exception stack trace:

java.lang.NullPointerException? at descent.internal.core.JarPackageFragmentRoot?.computeChildrenOfFile(JarPackageFragmentRoot?.java:109) at descent.internal.core.JarPackageFragmentRoot?.computeChildren(JarPackageFragmentRoot?.java:78) at descent.internal.core.JavaProjectElementInfo?.getProjectCache(JavaProjectElementInfo?.java:215) at descent.internal.core.JavaProjectElementInfo?.newNameLookup(JavaProjectElementInfo?.java:286) at descent.internal.core.JavaProject?.newNameLookup(JavaProject?.java:2559) at descent.internal.core.SearchableEnvironment?.<init>(SearchableEnvironment?.java:50) at descent.internal.core.SearchableEnvironment?.<init>(SearchableEnvironment?.java:64) at descent.internal.core.JavaProject?.newSearchableNameEnvironment(JavaProject?.java:2584) at descent.internal.core.Openable.codeComplete(Openable.java:129) at descent.internal.core.CompilationUnit?.codeComplete(CompilationUnit?.java:283) at descent.internal.core.CompilationUnit?.codeComplete(CompilationUnit?.java:276) at descent.internal.ui.text.java.JavaCompletionProposalComputer?.internalComputeCompletionProposals(JavaCompletionProposalComputer?.java:203) at descent.internal.ui.text.java.JavaCompletionProposalComputer?.computeCompletionProposals(JavaCompletionProposalComputer?.java:183) at descent.internal.ui.text.java.CompletionProposalComputerDescriptor?.computeCompletionProposals(CompletionProposalComputerDescriptor?.java:303) at descent.internal.ui.text.java.CompletionProposalCategory?.computeCompletionProposals(CompletionProposalCategory?.java:264) at descent.internal.ui.text.java.ContentAssistProcessor?.collectProposals(ContentAssistProcessor?.java:251) at descent.internal.ui.text.java.ContentAssistProcessor?.computeCompletionProposals(ContentAssistProcessor?.java:220) at org.eclipse.jface.text.contentassist.ContentAssistant?.computeCompletionProposals(ContentAssistant?.java:1759) at org.eclipse.jface.text.contentassist.CompletionProposalPopup?.computeProposals(CompletionProposalPopup?.java:478) at org.eclipse.jface.text.contentassist.CompletionProposalPopup?.access$16(CompletionProposalPopup?.java:475) at org.eclipse.jface.text.contentassist.CompletionProposalPopup?$2.run(CompletionProposalPopup?.java:410) at org.eclipse.swt.custom.BusyIndicator?.showWhile(BusyIndicator?.java:67) at org.eclipse.jface.text.contentassist.CompletionProposalPopup?.showProposals(CompletionProposalPopup?.java:404) at org.eclipse.jface.text.contentassist.ContentAssistant?$2.run(ContentAssistant?.java:354) at org.eclipse.swt.widgets.RunnableLock?.run(RunnableLock?.java:35) at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:123) at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3659) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3296) at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2389) at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2353) at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2219) at org.eclipse.ui.internal.Workbench$4.run(Workbench.java:466) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:289) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:461) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:106) at org.eclipse.equinox.internal.app.EclipseAppHandle?.run(EclipseAppHandle?.java:169) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher?.runApplication(EclipseAppLauncher?.java:106) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher?.start(EclipseAppLauncher?.java:76) at org.eclipse.core.runtime.adaptor.EclipseStarter?.run(EclipseStarter?.java:363) at org.eclipse.core.runtime.adaptor.EclipseStarter?.run(EclipseStarter?.java:176) at sun.reflect.NativeMethodAccessorImpl?.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl?.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl?.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:508) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:447) at org.eclipse.equinox.launcher.Main.run(Main.java:1173)

session data

eclipse.buildId=M20071023-1652 java.version=1.6.0_03 java.vendor=Sun Microsystems Inc. BootLoader? constants: OS=win32, ARCH=x86, WS=win32, NL=de_DE Command-line arguments: -os win32 -ws win32 -arch x86

This should be fixed.