While I testing teiid I got the exception:

java.lang.ClassNotFoundException: org.drools.eclipse.action.ConvertToBPMN2ProcessAction
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:506)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:422)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:410)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at org.eclipse.osgi.internal.loader.BundleLoader.loadClass(BundleLoader.java:338)
at org.eclipse.osgi.framework.internal.core.BundleHost.loadClass(BundleHost.java:232)
at org.eclipse.osgi.framework.internal.core.AbstractBundle.loadClass(AbstractBundle.java:1197)
at org.eclipse.core.internal.registry.osgi.RegistryStrategyOSGI.createExecutableExtension(RegistryStrategyOSGI.java:174)
at org.eclipse.core.internal.registry.ExtensionRegistry.createExecutableExtension(ExtensionRegistry.java:904)
at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:243)
at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:55)
at org.eclipse.ui.internal.WorkbenchPlugin.createExtension(WorkbenchPlugin.java:259)
at org.eclipse.ui.internal.PluginAction.createDelegate(PluginAction.java:122)
at org.eclipse.ui.internal.PluginAction.selectionChanged(PluginAction.java:275)
at org.eclipse.ui.internal.PluginAction.<init>(PluginAction.java:112)

Can't say exact steps.