So, it did turn out that I was requesting Session State from all HTTP Handlers in my application and this was causing the CE Editor instantiation to fail. Which must mean that CE does not implement IRequiresSessionState. So, I moved my session handler to Application_PreRequestHandlerExecute and forced it to check for IRequireSessionState or IReadOnlySessionState. That fixed it.
Old Code:
void Application_AcquireRequestState(object sender, EventArgs e)
{
CheckIfLoggedIn();
}
New Code:
protected void Application_PreRequestHandlerExecute(Object sender, EventArgs e)
{
if (Context.Handler is IRequiresSessionState || Context.Handler is IReadOnlySessionState)
{
CheckIfLoggedIn();
}
}
void Application_AcquireRequestState(object sender, EventArgs e)
{
}