If you are stuck inside on a treadmill or trainer, turn up the heat. But, only if you are at your own house as the other patrons at a health club might not enjoy an impromptu sauna and the management probably wouldn't look to kindly on you melting their clientele either. I guess it seemed to help. In either case, whether adding extra layers or turning up the heat, be sure to drink much more water than you usually do. An electrolyte drink would be a good idea as well.
Nobody likes a shriveled up, dehydrated triathlete.
My butt hurts from riding my bike. The simple way to stop the old bike butt pain is to stop riding your bike, but that makes it hard to train for and race triathlons and duathlons. Try different bike seats - those ones with the hole in the center can be pretty cozy. Some bike shops will even let you try out seats and return them for others until you find the one you like. Make sure you are fitted properly on your bike.