So over the past couple of times that I've been developing a GAT package I've had the register package option disappear from the context menu. At first I thought my package was corrupt or I had done something silly so I would usually start a new package and cut and paste back to where I was. This morning it happened again... doh! but instead of rebuilding the package I had a look inside the Guidance Package Manager and noticed that no packages were enabled, one click to select my required guidance package and I was back up and running.
I'm sure I should have spotted this before, but maybe this will save someone else rebuilding a package unnecessarily