Matthew Fort, The Guardian 2009 shares his advice on this topic (http://www.guardian.co.uk/lifeandstyle/2009/jun/20/food-for-fort)
"A high number of food poisoning cases are indeed caused by reheated rice. Or perhaps I should say inadequately heated. It's not actually the reheating that's the problem - it's the way the rice has been stored before reheating. Uncooked rice can contain spores of Bacillus cereus, a bacteria that can cause food poisoning. Unless the rice is cooked properly, the spores can survive, and if you then leave it standing at room temperature for any length of time, the spores can germinate into bacteria. These will then multiply and may produce toxins that cause all manner of nasty side-effects. Reheating the rice won't get rid of these toxins, so the longer cooked rice is left at room temperature, the more likely it is that bacteria, or the toxins they produce, could stop the rice being safe to eat. Rice is best served when it has just been cooked, anyway, but if that's not possible, cool it as soon as you can (within an hour) and keep in the fridge for no more than a day. As when reheating any food, check it's steaming hot all the way through, and don't reheat more than once."