I've done some testing with Kepler SR1 and M2E 1.5.0.20140423-1440. My local repository location and nexus repository and mirror setup are picked up nicely: artifact download and workspace build work correctly.
There is however a problem with the run as maven actions: run as/maven install produces an error dialog like this (I hope the embedded images come through on the mailing list):
And 'run as/maven build ....' fails silently inside eclipse but produces the following on the workspace .log:
!ENTRY org.eclipse.ui 4 0 2014-04-24 10:45:21.704
!MESSAGE Unhandled event loop exception
!STACK 0
java.lang.IllegalArgumentException: Argument cannot be null
at org.eclipse.swt.SWT.error(SWT.java:4378)
at org.eclipse.swt.SWT.error(SWT.java:4312)
at org.eclipse.swt.SWT.error(SWT.java:4283)
at org.eclipse.swt.widgets.Widget.error(Widget.java:472)
at org.eclipse.swt.widgets.Text.setMessage(Text.java:2029)
at org.eclipse.m2e.ui.internal.launch.MavenLaunchMainTab.initializeFrom(MavenLaunchMainTab.java:499)
at org.eclipse.debug.ui.AbstractLaunchConfigurationTabGroup.initializeFrom(AbstractLaunchConfigurationTabGroup.java:86)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupWrapper.initializeFrom(LaunchConfigurationTabGroupWrapper.java:194)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupViewer.displayInstanceTabs(LaunchConfigurationTabGroupViewer.java:755)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupViewer$8.run(LaunchConfigurationTabGroupViewer.java:626)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupViewer.inputChanged(LaunchConfigurationTabGroupViewer.java:643)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupViewer.setInput0(LaunchConfigurationTabGroupViewer.java:605)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationTabGroupViewer.setInput(LaunchConfigurationTabGroupViewer.java:581)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationPropertiesDialog.initializeContent(LaunchConfigurationPropertiesDialog.java:102)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationsDialog.createContents(LaunchConfigurationsDialog.java:439)
at org.eclipse.jface.window.Window.create(Window.java:432)
at org.eclipse.jface.dialogs.Dialog.create(Dialog.java:1104)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationsDialog.create(LaunchConfigurationsDialog.java:370)
at org.eclipse.jface.window.Window.open(Window.java:791)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationsDialog.open(LaunchConfigurationsDialog.java:1134)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchConfigurationPropertiesDialog.open(LaunchConfigurationPropertiesDialog.java:203)
at org.eclipse.debug.ui.DebugUITools.openLaunchConfigurationDialog(DebugUITools.java:687)
at org.eclipse.m2e.actions.ExecutePomAction.launch(ExecutePomAction.java:157)
at org.eclipse.m2e.actions.ExecutePomAction.launch(ExecutePomAction.java:127)
at org.eclipse.debug.internal.ui.launchConfigurations.LaunchShortcutExtension.launch(LaunchShortcutExtension.java:434)
at org.eclipse.debug.internal.ui.actions.LaunchShortcutAction.run(LaunchShortcutAction.java:73)
at org.eclipse.debug.internal.ui.actions.LaunchShortcutAction.runWithEvent(LaunchShortcutAction.java:121)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1081)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1066)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:778)
at org.eclipse.jface.action.ActionContributionItem$9.handleEvent(ActionContributionItem.java:1284)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1057)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4170)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3759)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1113)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:997)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:138)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:610)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:567)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:354)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:181)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:636)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:591)
at org.eclipse.equinox.launcher.Main.run(Main.java:1450)
at org.eclipse.equinox.launcher.Main.main(Main.java:1426)
It doesn't change anything in the errors if I switch to the EMBEDDED installation.
Is there some other information I can provide to help you in pinpointing this problem?