jon121, I tried to reproduce the problem and the composition saved OK for me (no errors).
Did you make any changes to the composition before saving?
That error message could indicate that you somehow ended up with a published port whose data type is Generic. Vuo is supposed to prevent you from doing that, but if it doesn't, then you can delete and recreate the published port.
Currently, when you double-click on a subcomposition node, the subcomposition opens in a new window. This feature request would add an alternative way of opening the subcomposition. When opened this way, the subcomposition would be embedded within the original composition. You would still see the subcomposition node in the context of the original composition, but it would be enlarged / X-rayed so you could also see the contents of the subcomposition.
