P5Q Turbo 8g memory trbl

Go into the Bios and manually set all of your timings and voltages to the maker's recommended. Ensure the Command Rate is set to 2T, and in the advanced options: Ensure tRFC ("Refresh to Activate Delay" - sometimes named differently) is set to 54 or greater.

Also - 8GB is a LOT of memory, you may need to accept that your board won't run it all at 1066.

Have you tried running the 8GB at 800Mhz? I know my Mobo (DFI LP P35 T2R) will happily run 4GB at 1066, but is much less than happy doing that with 8 (though in this case I could make it work). But it bugged me that I had to push the board and front side buss as hard as I was in order to run that much memory that fast. So I dialed the RAM down to DDR2 800, and have been running nice tight cas 4 timings for the better part of the last 2 years.

So - Food for thought: You might want to try DDR2 800, instead of the 1066 you currently have. I promise you, you'll only be able to tell the difference in artificial benchmarks.