If you get one of the following errors : The type org.eclipse.core.runtime.IAdaptable cannot be resolved. It is indirectly referenced from required .class files. The type org.eclipse.core.runtime.CoreException cannot be resolved. It is indirectly referenced from required .class files. First of all, check that your plugins depend on org.eclipse.core.runtime plugin. The classes above are located in org.eclipse.equinox.common plugin, and should be included (along with org.eclipse.core.runtime plugin) in your target platform. If it still occurs, most likely you get your target platform plugins mixed up. I got this error because I tried to mix plugins from my Eclipse IDE installation (Helios 3.6-SR-1) with Eclipse 3.7M4 Platform plugins. Simply unchecking the plugins from target platform Contents tab is not enough. I have to actually remove the location. If you notice duplicate plugins in your Target Platform Definition's Contents tab, then you're getting this problem. Remove the offending plugins location from the target platform definition. If you must add plugins from Eclipse IDE location, cherry pick each plugin from the Locations UI, instead of just adding the whole SDK and unchecking them from the Contents tab.