AM2 SMP Kernel 2.6.21 Hangs

I am using slackware 10.2 - with a custom compiled kernel (initially
2.6.16 - but now upgraded to latest 2.6.21) 

Hardware listed below..
 
CPU    : AMD Athlon 64 X2 4600
MB     : NF-M2 nView -
http://www.abit-usa.com/products/mb/products.php?categories=1&model=327
Memory : 2GB PATRIOT PC6400 800Mhz
Other  : Adaptec UWSCSI 2940
         Adaptec 2610SA Sata raid card

After installing the new cpu / mb initially with the 2.6.16 kernel I had
to add the noapic boot setting to the Kernel to work. After this the
machine will work for a while but I it will hang after an hour or so.
With either kernel panics / segmentation faults or just lock up
completely with no error messages. 

I have run memtest86 and the memory all seems fine.

I have now updated to the latest kernel (2.6.21) and I can now boot with
out using the noapic boot option, but I am still having the same
problems with the system hanging after an hour or so. I have also tried
recompiling with kernel with various different settings :-

	without smp support ( still crashes )
	without my MB chipset / graphics drivers compiled in.

Does anyone have any ideas of anything else I could try?

Thanks
Toby