From wikipedia
http://en.wikipedia.org/wiki/Beans
about the toxins in beans:
Some kinds of raw beans and especially red and kidney beans, contain a harmful toxin (the lectin Phytohaemagglutinin) that must be destroyed by cooking. A recommended method is to boil the beans for at least ten minutes; undercooked beans may be more toxic than raw beans.[7] Cooking beans in a slow cooker, because of the lower temperatures often used, may not destroy toxins even though the beans do not smell or taste 'bad'[7] (though this should not be a problem if the food reaches boiling and stays there for some time).
and then this bit is under 'common bean'
Before they are eaten, the raw bean seeds should be soaked in water for several hours and then boiled for at least ten minutes in new fresh water to degrade a toxic compound — the lectin phytohaemagglutinin — found in the bean, which would otherwise cause severe gastric upset. This compound is present in many varieties (and in some other species of bean), but is especially concentrated in red kidney beans and white kidney beans (Cannellini beans). Although in the case of dry beans the ten minutes required to degrade the toxin is much shorter than the hours required to fully cook the beans themselves, outbreaks of poisoning have been associated with the use of slow cookers whose low cooking temperatures may be unable to degrade the toxin. Sprouts of pulses high in haemaglutins should not be eaten. Kidney beans, especially, should not be soaked or sprouted