Problem Running RoboRunner

I'm finally at the point where I am trying to actually launch RoboRunner. Currently running into an error I will have to debug. Posting part of the stack trace here in case anyone wants to comment.

Copying missing bots... 0 JAR copies done!
Initializing engine: robocodes\z1... Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at robowiki.runner.BattleRunner.initEngine(BattleRunner.java:66)
	at robowiki.runner.BattleRunner.<init>(BattleRunner.java:42)
	at robowiki.runner.RoboRunner.<init>(RoboRunner.java:172)
	at org.xandercat.roborunner.runner.RoboRunnerService.startRunner(RoboRunnerService.java:44)
	at org.xandercat.roborunner.runner.action.LaunchRoboRunnerAction.actionPerformed(LaunchRoboRunnerAction.java:46)
	at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)

And the chunk of relevant code from RoboRunner:

      System.out.print("Initializing engine: " + enginePath + "... ");
      ProcessBuilder builder = new ProcessBuilder(command);
      builder.redirectErrorStream(true);
      Process battleProcess = builder.start();
      BufferedReader reader = new BufferedReader(
          new InputStreamReader(battleProcess.getInputStream()));
      String processOutput;
      do {
        processOutput = reader.readLine();
      } while (!processOutput.equals(BattleProcess.READY_SIGNAL));
      System.out.println("done!");
      _processQueue.add(battleProcess);

Presumably, the input stream never provided the BattleProcess.READY_SIGNAL. I'll have to do some digging to figure out why. I'm not entirely clear on what the RoboRunner requirements are, but at the moment I am running it under Java 6 with Robocode 1.7.3.0.

FYI -- line 66 is the while part of the do/while loop.

I'll take a deeper look later when I'm home. At a glance, it seems like processOutput is coming up null - maybe the condition should be "processOutput != null && ...". What command are you using to launch this?