Hi Theint,
The SCG using 2.5.0 will NOT be able to control a T300 running the 2.5.1 firmware. I would advise you to upgrade your vSCG to the latest 3.0.4 code release available on the support site.
This code release will require you to create a NEW VM instance and migrate any of your configurations and licenses across. Please contact your local partner or support if you require assistance.