Tamed wolves will no longer be able to stand (nothing happens when you right-click them) if they are left sitting for an extended period of time, and if one is struck with anything by the player they all start to growl as though they were hostile, but they remain sitting and don't change appearance. This has happened in every version of Minecraft that I have played, from before the release of 1.0 to 1.4.5.

This also appears to happen with cats, accept that they don't become hostile, they just don't do anything when you right click on them if they are left sitting for an extended period of time.