Why does MVN return -1 on successful build?

Question

I'm running Maven 2.2.1 and it's returning an exit code of -1 even though it states that the build is successful. Anyone know what causes this exit code to occur as it's breaking our build process?

As a further tidbit of information MVN is being called from our MS TFS build server which is where this problem occurs. If I can MVN from the command line the exit code is 0.

Here's the Reactor Summary:

[INFO] ------------------------------------------------------------------------
  [INFO] Reactor Summary:
  [INFO] ------------------------------------------------------------------------
  [INFO] Aquarius Web App ...................................... SUCCESS [6.655s]
  [INFO] Aquarius Flex Library ................................. SUCCESS [1:26.329s]
  [INFO] Aquarius Flex Application ............................. SUCCESS [31.412s]
  [INFO] Aquarius Web Archive .................................. SUCCESS [5:22.484s]
  [INFO] ------------------------------------------------------------------------
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD SUCCESSFUL
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 8 minutes 34 seconds
  [INFO] Finished at: Mon Oct 25 10:19:50 BST 2010
  [INFO] Final Memory: 62M/225M
  [INFO] ------------------------------------------------------------------------