From the VIA C3 EBGA Datasheet:
"The EBGA VIA C3 is specified for operation with device case temperatures in the range of 0°C to 85°C."
"device case" here means the physical package on the motherboard in which the CPU is embedded, not your case's ambient temperature. Your temperature reading seems to be within reason. Mine runs at 32°C at idle and about 65°C at 100% usage. I'm using the Travla-C137 case.
A good free tool to use for tracking your CPU and case temps, plus other goodies is Motherboard Monitor 5. Check here...
http://mbm.livewiredev.commeb