v4.5.2: edu.internet2.middleware.grouper.app.provisioning.GrouperProvisioningService#calculateProvisioningAttributes

2095      while (true) {

2096        depth++;

2097        currObjectName = GrouperUtil.parentStemNameFromName(currObjectName);

2098        if (currObjectName == null) {

2099          break;

2100        }

...

If it's the root stem, currObjectName is "" rather than null, so the loop never exits until the cpu catches fire.