i think it has something to do with the dual channel capabilities of your motherboard. Basically, dual channel ram is like a RAID array. In a RAID array, you have to have two hard drives (or more, but we'll stick to two), both of equal size and speed etc, if there not of equal size then you'll just end up losing some space (so say you had a 40gb hard drive and a 60gb in a RAID array, you would lose 20gb). So RAID-0 (or stripping), you store half of each file on each drive, so splitting the work load. Same applies for dual channel ram, they share the load, and so make your system faster.
The reason they work on the AMD syatem is that it won't support dual channel ram and so you can stick in different types etc without any difficulty.
I've never worked with a dual channel machine before but i'd think there would be an option in the bios (press delete when you start the machine) to turn it off. Failing that, look at the manual, because i'm 99% sure its something to do with it being dual channel. Post back the results.