I've been experiencing some real life breakdowns. As I type my car is being looked at by the mechanics who will probably tell me I need a new alternator. In a purely defensive exercise I've been trying to think of how this sort of thing could impact a game.
There aren't any alternators in D&D of course, but there are methods of transport that can break down. Ships can lose a mast, horses can throw a shoe, wagons (with loot!) can break a wheel. How does this slow down your group, how do they handle this? What if someone comes down with an intestinal bug, or eats some bad cheese? Something that healing magic wont handle, but is really only a relatively minor inconvenience.
In 4ethis is the sort of event that can be handled with a skill challenge, and maybe a loss of a healing surge during the next encounter. In older D&D this is the sort of thing that could be role-played out. The thing about this sort of scene/encounter/challenge is that it forces you to make a choice. Do you slow down, stop, keep going, do you try to fix it yourself, or pay to have it fixed? Are people going to try to rip you off when you're in dire straights?
I've heard back from the garage, and and it is the alternator, and now I'm spending $500 more than I was planning on.