Here is the stack trace from the PDE error log.
org.eclipse.core.runtime.AssertionFailedException: null argument:
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:84)
at org.eclipse.core.runtime.Assert.isNotNull(Assert.java:72)
at org.eclipse.core.runtime.Path.initialize(Path.java:575)
at org.eclipse.core.runtime.Path.<init>(Path.java:162)
at org.objectstyle.wolips.variables.VariablesPlugin.fixMissingSeparatorAfterDevice(VariablesPlugin.java:171)
at org.objectstyle.wolips.variables.VariablesPlugin.getSystemRoot(VariablesPlugin.java:185)
at org.objectstyle.wolips.launching.delegates.WOJavaLocalApplicationLaunchConfigurationDelegate.getProgramArguments(WOJavaLocalApplicationLaunchConfigurationDelegate.java:222)
at org.eclipse.jdt.launching.JavaLaunchDelegate.launch(JavaLaunchDelegate.java:63)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:759)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:608)
at org.eclipse.debug.internal.ui.DebugUIPlugin.buildAndLaunch(DebugUIPlugin.java:899)
at org.eclipse.debug.internal.ui.DebugUIPlugin$7.run(DebugUIPlugin.java:1102)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)