Hi,
Not sure if you've solved this yet, but I'll throw in my tuppence.
I had a similar problem. By default, the mobo reads the SPD information from the Corsairs, and this tells the motherboard that they are 800Mhz sticks. However, there is EPP information there too, which will tell the motherboard to run them at 1066. You need to tell the mobo to read this instead of the SPD.
In my case, this meant an option in the BIOS called Enable EPP Support, or something like that. I don't know what it will say in yours, but you need to look for something to do with EPP.
This should sort you out, if the problem is the same as mine, and you won't need to fiddle about with anything else.
Hope this helps.