It is generally known that in the presence of multiple node or communication failures atomic commit protocols cannot avoid blocking. While in fixed wired networks such situations are rare because of low failure probabilities, mobile ad-hoc networks (MANETs) are considered to be a more challenging environment. In this technical report I present a probabilistic model to predict the abort and blocking risk of distributed atomic transactions for arbitrary MANET scenarios. The model presented is applied to a standard MANET scenario to demonstrate the dimensions of blocking risks to be expected in MANETs.