Hey everyone,
Figure I'd update this, in case anyone comes across this issue as well.
In my code, I was rebuilding the player gameobject, as sent from my server. The rebuilt GO had a tk2dSprite component on it already, with a valid texture.
Instead of using the code to switch to modelID+1 then back to modelID, I'm now adding a new tk2dSprite component to it.
(As such, I've removed the tk2dSprite component from the server template, and am also adding the component on the server)