Hi @jubalrahl, Ember has definitely seen a lot of change in the 12 months since printing, so it is quite possible one of the dependencies has made a breaking change (x-select definitely broke some things). Which error are you getting? The error from x-select or an error POSTing to the Tracker server?
Here is a thread from errata about switching to the newer x-select, hope it helps! Install EmberX-Select p.437