For some reason when planning a Sprint that contains Custom Issue Types, the Custom Issues that I have created do not allow me to add an Estimate as part of the Sprint Planning Phase, however the 'normal' Issue Types (Task, etc) allow me to enter an Estimate.
I've double checked to make sure that my Custom Issue is using the same Field Scheme, Issue Type Scheme, and Screen Scheme (See attached) as the Task that allows me to enter an Estimate, yet for some reason the Estimate field does not appear. 
