One of my biggest pet peeves is the scenario - most frequently seen in romantic comedy movies, but it also infects the written word - where character A is keeping a secret from character B; A is on the verge of finally confessing the secret, but is too late, because B has just discovered it; and B storms out without waiting for an explanation.
This is most frequently used between romantic partners, and it makes my eyes cross. Really? You're falling in love with someone, and you can't bring yourself to stop and talk things out? You care about a person, but you have no ability to consider things from their perspective and attempt to understand their reasons? It doesn't quite snap my suspension of disbelief (usually), but it does tend to make me think that one or the other character is actually an idiot. (Hence the term "idiot plot," I suppose.)
In similar vein, I have a little trouble conceiving of characters who are generally friendly to each other who can't attempt to put themselves in the other's shoes. This flexibility of viewpoint, to me, seems a necessary part of humanity - certainly of sympathetic characters! So there are times when I have trouble creating interpersonal conflicts between my characters because they really will stop and talk things out reasonably ... unless they're being shot at or otherwise forced to end the conversation prematurely.
Come to think of it, I did that multiple times in Scylla and Charybdis without thinking about it: two characters clash over a misunderstanding, but before it can be sorted out, circumstances wrench them apart.
Of course, this can also be overused to the point of ridicule ... but at least it's a different problem!