Today is the only time i have had it on auto or in case of my board use spd.
Although we both have kingston DDR 400 mine are 1 gig modules and quite frankly there are loads of manufacturers that the actual chips could have been made by, I think samsung is a favourite of kingston but certainly not the only one they use. You could only say we have the same memory if we compared numbers printed on actual chips.

I have set the memory slower than the spd setting but it never occured to me before that it might have something to do with firmware, I maybe totally barking up the wrong tree, I don't even know if osx does read memory firmware or if this is done purely by efi. But hell this seems to be the best "stablest" yet so who knows.