SoapUI plugin to Intellij Idea not working

Hi,
I installed SoapUI to my Intellij Idea from Intellij Repositories and when I want to start SoapUI, no class found exception is thrown:

com/intellij/peer/PeerFactory: com/intellij/peer/PeerFactory
java.lang.NoClassDefFoundError: com/intellij/peer/PeerFactory
at com.eviware.soapui.intellij.plugin.SoapUIPlugin.initToolWindow(SoapUIPlugin.java:270)
at com.eviware.soapui.intellij.plugin.SoapUIPlugin.init(SoapUIPlugin.java:114)
at com.eviware.soapui.intellij.plugin.actions.ShowHideSoapUI.actionPerformed(ShowHideSoapUI.java:42)
at com.intellij.openapi.actionSystem.ex.ActionUtil.performActionDumbAware(ActionUtil.java:164)
at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter$1.run(ActionMenuItem.java:261)
at com.intellij.openapi.wm.impl.FocusManagerImpl.runOnOwnContext(FocusManagerImpl.java:923)
at com.intellij.openapi.wm.impl.IdeFocusManagerImpl.runOnOwnContext(IdeFocusManagerImpl.java:124)
at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.actionPerformed(ActionMenuItem.java:231)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at com.intellij.openapi.actionSystem.impl.ActionMenuItem.fireActionPerformed(ActionMenuItem.java:104)
at com.intellij.ui.plaf.beg.BegMenuItemUI.a(BegMenuItemUI.java:512)
at com.intellij.ui.plaf.beg.BegMenuItemUI.access$300(BegMenuItemUI.java:44)
at com.intellij.ui.plaf.beg.BegMenuItemUI$MyMouseInputHandler.mouseReleased(BegMenuItemUI.java:532)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at com.intellij.ide.IdeEventQueue.e(IdeEventQueue.java:697)
at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:520)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:335)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
Caused by: java.lang.ClassNotFoundException: com.intellij.peer.PeerFactory PluginClassLoader[soapUI Plugin, 3.5]
at com.intellij.ide.plugins.cl.PluginClassLoader.loadClass(PluginClassLoader.java:68)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 47 more

any ideas how to fix this?
Thanks