Non-carbon based life forms on hot planets
Given that a $\ce{C-C}$ bond dissociation energy is $83\ \mathrm{kcal\ mol^{-1}}$, and $\ce{Si-Si}$ bond dissociation energy is $52\ \mathrm{kcal\ mol^{-1}}$, a silicon based life form is much worse off on a high temperature planet. It's actually for this very reason that there aren't nearly as many silicon based compounds as there are carbon based compounds. Thats not to say they don't exist, however. There are silicon hydrides that in the form of silicon chains, analagous to alkanes, existing up to about 8 silicon long. They are all readily hydrolyzed and are thermally unstable, especially the longer chains.

Silicon is also not quite as versatile as carbon in terms of the types of bonds it can form. Carbon is capable of forming single, double, and triple bonds due to its ability to hybridize its $\mathrm{s}$ and $\mathrm{p}$ orbitals. Silicon is a larger atom than carbon, and as a result it is much more difficult for its $\mathrm{p}$-orbitals to overlap with the $\mathrm{p}$-oribatls of adjacent atoms. Again, this is of course not to say that this doesn't happen, as it does in the case of diselenes and disilynes, but again, these are (very) unstable.

Most often silicon is found combined with oxygen, as in the very stable $\ce{SiO2}$, or as you might know it: glass, sand, or quartz; not exactly ideal for a moving, living creature. Just an idea, but if you're trying to make scientifically feasible life forms on a hot planet, you might just be better off having carbon based life forms in an inert atmosphere. In other words, an atmosphere that doesn't lend to them bursting into flames.

I'm not sure how set you were on making these different races out of other elements, but no element by itself really matches the chemical variability that carbon offers.

EDIT: After doing a little more research, I thought it might be beneficial to include polysiloxanes, or silicone, which consist of $\ce{C-(Si-O)_{n}-Si-C}$ bonds. These actually are actually very interesting because they are extremely elastic, functional over a wide range of temperatures ($-100^\circ \mathrm{C}-300^\circ \mathrm{C}$), resistant to ozone and UV radiation, do not promote bacterial growth (but who knows about extraterrestrial bacteria), have a low chemical reactivity, high electrical resistivity, and most interestingly, have self-healing properties. 

I would now change my tune and say that maybe a race of silicon-carbon based life forms isn't too far fetched at all! At least for sci-fi writing purposes.