Have you tried using a programme called "Core Temp"
It apparently gives you a "better" CPU temp readout i.e. more accurate, but I and others have doubts.
Idle Smart Guardian gives me 29C for CPU while Core temp gives me both core temps as being 44 and 34 C, so much higher there, and load Smart Guardian gives me 40C and Core Temp gives me 60/52C for each core.
What does it read for you? Do you have a big difference between Core 0 and core 1?
Also are you dual priming that CPU? http://sp2004.fre3.com/beta/beta2.htm