NullPointerException generating report from command line

I am runnning automated tests from the command line in LoadUI. The tests run fine and I can see the results in the terminal. However if I try to generate a report using the -r flag I get a NullPointerException and no report. Error below:

14:13:49,976 ERROR [CommandRunner] An error occured when executing the script
java.lang.NullPointerException: Cannot get property 'label' on null object
at org.codehaus.groovy.runtime.NullObject.getProperty(NullObject.java:56)
at org.codehaus.groovy.runtime.InvokerHelper.getProperty(InvokerHelper.java:156)
at org.codehaus.groovy.runtime.callsite.NullCallSite.getProperty(NullCallSite.java:44)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:227)
at com.eviware.loadui.util.Script1.run(Script1.groovy:284)
at com.eviware.loadui.cmd.CommandRunner$CommandRunnable.run(CommandRunner.java:93)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

I'm running LoadUI 2.7.0 on Windows 7 64-bit. I've tried reinstalling 32 and 64 bit versions but get the same error.

The command I am using is:

loadui-cmd.bat -p F:\LoadUI\TestReports.xml -L 10:0:0 -r F:\LoadUI\Reports -f XML

I've tried various combinatons and different formats but get the same error.