running tests using command line

I'm trying to run the plugin tests using the command-line ant build, so far without success.

Invoking "ant run.tests" gives me:

(...initial output snipped...)
    run.tests:

     [copy] Copying 1477 files to C:\work\scala-plugin\classes\production\Scala\
testdata
     [echo] C:\Program Files\Java\jdk1.6.0_21\jre/lib/tools.jar
    [junit] WARNING: multiple versions of ant detected in path for junit
    [junit]          jar:file:/C:/jars/apache-ant-1.7.1/lib/ant.jar!/org/apache/
tools/ant/Project.class
    [junit]      and jar:file:/C:/Program%20Files%20(x86)/JetBrains/IntelliJ%20I
DEA%20102.149/lib/ant/lib/ant.jar!/org/apache/tools/ant/Project.class
    [junit] Running org.jetbrains.plugins.scala.annotator.ApplicationAnnotatorTe
st
    [junit] Tests run: 1, Failures: 0, Errors: 1, Time elapsed: 0 sec


BUILD FAILED
C:\work\scala-plugin\build.xml:367: Process fork failed.

Any suggestions? If my own version of Ant interfering perhaps?

Thanks,
-tt