Memory Frequencies dropping with 2 sticks?

I am hopping someone can offer some insight on this, cause i am out of Ideas.. I am running a Asus p4p800 deluxe (865pe), and had been running for some time with a single 512 XMS pc3200 cas-2 stick. it ran like a champ and registered at 400mhz. I just bought a new chip, of the same type and when i install that one, the memory frequency drops to 266mhz dual channel. pull it out, and i am back at 400mhz single with the old. so i tried 'em both seperatly.. and wonder of wonders, they both clock in at 400mhz single channel.. together again, 266mhz dual. switch banks, same thing... So I RMA'd the new chip. Got a new one, SAME THING AGAIN.. So I pulled the memory out of my other computer, two 256 twinx LLPT cas 2 pc3200's stuck them in and they work fine, showing up at boot as 400mhz dual channel.. I am running the latest bios of v.1016 for the MOBO and I have cut it down so that there are no special settings for the CPU or memory.. its straight vanilla.... I ran Sisoft Sandra and Aida32 to check the cas and frequencies of the two chips.. the only thing I can find different betwixt the two is that the old is listed as having the max latency at 2.5 (5ms @ 200mhz) and the newer chip says 3.0 (5ms @ 200mhz) however i thought ( unless I am mistaken) that they would just run together at the lowest performance rate. The only difference [U]on[/U] the chips is the revision , old one is as follows: CMX512-3200c2 XMS3202v1.1 0325054 New one : CMX512-3200c2 XMS3202v3.1 0427115-0 Help anyone? Smokey