Eclipse Luna - Project Explorer is empty after import

When I import or try to create a project in eclipse Luna I get the following error:

Errors occurred during build. The builder 'Java Builder' failed in project 'project-name'. loader constraint violation: loader (instance of org / eclipse / osgi / internal / loader / EquinoxClassLoader) previously bootstrapped for another type named "org / aspectj / runtime / internal / CFlowCounter" Errors performed by "Maven Project Builder" on project " project-name ". loader constraint violation: with permissive method "scala.tools.eclipse.contribution.weaving.jdt.jcompiler.BuildManagerAspect.ajc $ about $ scala_tools_eclipse_contribution_weaving_jdt_jcompiler_BuildManagerAspect $ 1 $ add4995 (Lorg / internal / eclipse events / Build / core / resources / iproject; lorg / AspectJ / runtime / internal / AroundClosure;) Lorg / eclipse / core / resources / IResourceDelta; "class loader (instance of org / eclipse / osgi / internal / loader / EquinoxClassLoader) of the current class, org / eclipse / core / internal / events / BuildManager and class loader (instance of org / eclipse / osgi / internal / loader / EquinoxClassLoader) for the resolved class, scala / tools / eclipse / contribution / weaving / jdt / jcompiler / BuildManagerAspect, have different class objects for type .weaving.jdt.jcompiler.BuildManagerAspect.ajc $ about $ scala_tools_eclipse_contribution_weaving_jdt_jcompiler_BuildManagerAspect $ 1 $ add4995 (lorg / eclipse / CORE / internal / events / BuildManager; lorg / eclipse / core / resources / iproject; Lorg / AspectJ / runtime / inner / AroundClosure / Lorg / eclipse resources /;) core / eclipse IResourceDelta; used in signature Errors running "Java Builder" in project 'test'. org / aspectj / runtime / internal / CFlowCounter Errors performed by builder 'Validation' in project 'test'. loader constraint violation: with permissive method "scala.tools.eclipse.contribution.weaving.jdt.jcompiler.BuildManagerAspect.ajc $ around $ scala_tools_eclipse_contribution_weaving_jdt_jcompiler_BuildManagerAspect $ 1 $ add4995 (Lorg / internal / eclipse events / Build core / core / resources / iproject; Lorg / AspectJ / runtime / internal / AroundClosure;) Lorg / eclipse / core / resources / IResourceDelta; " class loader (instance of org / eclipse / osgi / internal / loader / EquinoxClassLoader) of current class, org / eclipse / core / internal / events / BuildManager and class loader (instance of org / eclipse / osgi / internal / loader / EquinoxClassLoader) for resolved class ,scala / tools / eclipse / contribution / weaving / JDT / jcompiler / BuildManagerAspect, have different class objects for type .weaving.jdt.jcompiler.BuildManagerAspect.ajc $ about $ scala_tools_eclipse_contribution_weaving_jdt_jcompiler_BuildManager / weaving_jdt_jcompiler_BuildManager / weaving_jdt_jcompiler_contribution_weaving_jdt_jcompiler_contribution_weaving_jdt_jcompiler_contribution_weaving_jdt_jcompiler_contribution_weaving_jdt_jcompiler_contribution BuildManager; lorg / eclipse / core / resources / iproject; lorg / AspectJ / runtime / internal / AroundClosure;) lorg / eclipse / core / resources / IResourceDelta; used in signature) Lorg / eclipse / core / resources / IResourceDelta; used in signature) Lorg / eclipse / core / resources / IResourceDelta; used in signature

I checked the permissions and restarted eclipse but nothing worked for me.

Does anyone know / meet this error? how can i fix this?