Difference between vCO 5.5 Rest and vCO 6.0 Rest

I have a vCO 5.5 Cluster and a vCO 6.0 cluster that I am working with for my vCAC environment and most everything is working great but something has change with Rest calls between the version of vCO and the Rest Plkugin.  What works in vCO 5.5 is giving me this error on all my rest calls in vCO 6.0  [2015-02-11 10:46:54.380] [E] Connection pool shut down

Anyone seen this and know of the top of their head what has changed and how to adapt?

Thanks

Steve