I assume they meant they use the free version by same author as the popular, and possibly more accurate, but that is beside the point, of *Hardware Monitor*.
I'd try reinstalling whatever software you're running, I assume Temperature Monitor from Marcel Bresink. It's possible there's a SL update you didn't get yet. Also try Using his Hardware monitor in demo mode. I'm seeing my core temps clearly under Snow Leopard.
Also, sometimes quitting and restarting the monitor software helps. Several times if necessary. Temperature Monitor has some menu items that are helpful if readings don't display, like Rescan Sensor Configuration and Update All Readings Now. Try those.
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Temperature Monitor software and Snow Leopard
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