Erreur au build/lancement plugin

Bonjour,

je développe un plugin eclipse, et j'ai une erreur pendant le build automatique qui se lance une fois la nouvelle interface ouverte:

java.lang.ClassNotFoundException: org.eclipse.ajdt.core.builder.AJBuilder
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:402)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:347)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:83)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at org.eclipse.osgi.framework.internal.core.BundleLoader.loadClass(BundleLoader.java:278)
at org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:227)
at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:1245)
at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:147)
at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:759)
at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)
at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:51)
at org.eclipse.core.internal.events.BuildManager.instantiateBuilder(BuildManager.java:759)
at org.eclipse.core.internal.events.BuildManager.initializeBuilder(BuildManager.java:711)
at org.eclipse.core.internal.events.BuildManager.getBuilder(BuildManager.java:452)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:199)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:230)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:37)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:233)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:252)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:285)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:154)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:217)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:58)

après si je fait une clean all et que je refait un build sur tout alors l'erreur n'apparait pas.

par contre quand je lance mon appli j'ai l'erreur suivante:

java.lang.ClassNotFoundException: org.eclipse.ajdt.internal.ui.ajde.CachedRuntimeClasspathEntryResolver
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:402)
at org.eclipse.osgi.framework.internal.core.BundleLoader.findClass(BundleLoader.java:347)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:83)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at org.eclipse.osgi.framework.internal.core.BundleLoader.loadClass(BundleLoader.java:278)
at org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:227)
at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:1245)
at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:147)
at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:759)
at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)
at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:51)
at org.eclipse.jdt.internal.launching.RuntimeClasspathEntryResolver.getResolver(RuntimeClasspathEntryResolver.java:52)
at org.eclipse.jdt.internal.launching.RuntimeClasspathEntryResolver.resolveRuntimeClasspathEntry(RuntimeClasspathEntryResolver.java:44)
at org.eclipse.jdt.launching.JavaRuntime.resolveRuntimeClasspathEntry(JavaRuntime.java:901)
at org.eclipse.jdt.launching.StandardClasspathProvider.resolveClasspath(StandardClasspathProvider.java:75)
at org.eclipse.jdt.launching.JavaRuntime.resolveRuntimeClasspath(JavaRuntime.java:1182)
at org.eclipse.jdt.launching.AbstractJavaLaunchConfigurationDelegate.getClasspath(AbstractJavaLaunchConfigurationDelegate.java:415)
at org.eclipse.pde.internal.ui.launcher.SWTLaunchConfiguration.getClasspath(SWTLaunchConfiguration.java:292)
at org.eclipse.pde.internal.ui.launcher.SWTLaunchConfiguration.launch(SWTLaunchConfiguration.java:104)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:639)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:565)
at org.eclipse.debug.internal.ui.DebugUIPlugin.buildAndLaunch(DebugUIPlugin.java:754)
at org.eclipse.debug.internal.ui.DebugUIPlugin$6.run(DebugUIPlugin.java:944)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:58)

merci de votre aide