vCenter Orchestrator and vCAC 5.2 Help

I'm trying to pull the Guest Operating system from VCAC using vCO. I started with a simple System.log statement in the Scriptable Task but it continues to return null. I can walk through the inventory in vCO and I see the field I'm looking for.

Input Parameter  = vCACVm         - Type: VCAC:VirtualMachine

System.log ("vCAC VM guest OS : " + vCACVm.guestOS);

The log displays:

[2014-05-29 08:13:14.227] [I] vCAC VM guest OS : null

Any ideas what I could be doing wrong?