Leadtek NCR18Dpro and Corsair VS512MB400 Compatiblity

I have a leadtek [B]K7NCR18DPRO[/B] nforce2 motherboard and just bought Corsair Value Select [B]VS512MB400[/B] LOT 04020730. I bought them from Outpost as a 2 piece kit for total of 1GB. On reciept (if i remember right) it listed them as [B]VS512MB400KIT[/B]. The problem is that I get major instabliity. It locks up and I get major graphic issues in any game. (but works if switch back to older memory) I have adjusted the bios to SPD. I have tried 3-4-4-8 settings I have tried 2.5-3-3-7 settings. I run these in Dual channel mode but tried slots 2&3 and 1&3 (leadtek manual says to run this way) Nothing I try except going back to my old memory works. Crucial PC 2100 memory. Every game works. No more lock ups. The manual says it must use 128bit DDR memory up to 3GB. It says it should be unbuffered. I downloaded memtest and will run overnight. I don't know whether to RMA? Or ask if Corsair will swap me for the correct modules if they are incompatible? (and pay difference if there is one) Please advise me on how to handle. thanks, Christopher