We consider Boolean models of the dynamics of interacting genes. Stability is defined for a large Boolean network by imagining two system states that are initially close in the sense of Hamming distance and asking whether or not their evolutions lead to subsequent divergence or convergence. We find a general method for answering this question and investigate the impact on stability of various factors,such as network topology (including assortitivity, community structure, small motifs, etc.), nodal dynamics, link delay times, and correlation between topological and nodal properties. We also introduce and discuss a hypothesis that orbital instability might be a causal contributor to the occurence of cancer. Reference: A.Pomerance, E.Ott, M.Girvan, W.Losert, Proc. Nat. Acad. Sci vol. 106, p. 8209 (2009).