Fan noise and weird CPU temperature

Hi,

All of a sudden my MacPro 2008 has gone fan crazy! The CPU and Exhaust fans are running about 2,500rpm and from iSTAT NANO and XRG are saying that the CPU DIE 1 is running at 108degree C (!!!) while the other cores are running at 25 to 30. I opened the mac and checked the heat sinks but they weren't hot at all.

Have a look at this image:
http://greydust.com/files/macpro.png

* I reset the PRAM and SMC (several times) but nothing has worked.
* Cleaned any dust using my Rocket Blower.
* Removed some RAM
* Reinstalled Lepoard
* Loaded into windows xp
* I done the Apple Hardware Test and it FAILED


I don't have apple care (stupid stupid!) so if anyone knows what is wrong before I have to shell loads of money I will be very grateful

Apple Hardware Test:

Last Run: 04/10/4009 18:13
Version: 3A142
Test Suite: Extended Test
Loop Count: 1
Result: Failed
Failure Code: 4SNS/1/40000000: TCBH-111.125

Basically I've done everything I know possible...

PLEASE HELP!!!

Thanks,
Hal