Hi, I have just started trying out Drools and having an issue trying to run the sample applications under Eclipse Helios with Groovy installed. When I try run any sample Drools application I get the stack trace shown below. I have looked around extensively on Google for assistance but have been unable to find any thing that has helped me determine what the issue is. Any suggestions would be appreciated. Regards -- Build groovy files option has not been set one way or the other: use 'options.put(CompilerOptions.OPTIONG_BuildGroovyFiles, CompilerOptions.ENABLED);' java.lang.NoClassDefFoundError: org/eclipse/core/runtime/Plugin         at java.lang.ClassLoader.defineClass1(Native Method)         at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)         at java.lang.ClassLoader.defineClass(ClassLoader.java:615)         at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)         at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)         at java.net.URLClassLoader.access$000(URLClassLoader.java:58)         at java.net.URLClassLoader$1.run(URLClassLoader.java:197)         at java.security.AccessController.doPrivileged(Native Method)         at java.net.URLClassLoader.findClass(URLClassLoader.java:190)         at java.lang.ClassLoader.loadClass(ClassLoader.java:306)         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)         at java.lang.ClassLoader.loadClass(ClassLoader.java:247)         at org.eclipse.jdt.internal.compiler.Compiler.initializeParser(Compiler.java:737)         at org.eclipse.jdt.internal.compiler.Compiler.<init>(Compiler.java:294)         at org.eclipse.jdt.internal.compiler.Compiler.<init>(Compiler.java:159)         at org.drools.commons.jci.compilers.EclipseJavaCompiler.compile(EclipseJavaCompiler.java:364)         at org.drools.commons.jci.compilers.AbstractJavaCompiler.compile(AbstractJavaCompiler.java:51)         at org.drools.rule.builder.dialect.java.JavaDialect.compileAll(JavaDialect.java:366)         at org.drools.compiler.DialectCompiletimeRegistry.compileAll(DialectCompiletimeRegistry.java:55)         at org.drools.compiler.PackageRegistry.compileAll(PackageRegistry.java:69)         at org.drools.compiler.PackageBuilder.compileAll(PackageBuilder.java:674)         at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:633)         at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:278)         at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:451)         at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:28)         at com.sample.DroolsTest.readKnowledgeBase(DroolsTest.java:40)         at com.sample.DroolsTest.main(DroolsTest.java:23) Caused by: java.lang.ClassNotFoundException: org.eclipse.core.runtime.Plugin         at java.net.URLClassLoader$1.run(URLClassLoader.java:202)         at java.security.AccessController.doPrivileged(Native Method)         at java.net.URLClassLoader.findClass(URLClassLoader.java:190)         at java.lang.ClassLoader.loadClass(ClassLoader.java:306)         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)         at java.lang.ClassLoader.loadClass(ClassLoader.java:247)         ... 27 more -- View this message in context: http://drools.46999.n3.nabble.com/Eclipse-Groovy-and-Drools-java-lang-NoC... Sent from the Drools: User forum mailing list archive at Nabble.com.