oops, i did it....
i have re-applied thermal paste with artic silver 5. My macbook air rev c 2,13ghz 128ssd runs at 40ºC in idle mode (no tasks, only dashboard with istat to view the temperature)
in light browsing (no flash) i read 50ºC with fans running at 2500, and in heavy usage (both cores at 100%) temperature reaches 82º
i'm running snow leopard build 10A402a