I'm having this same sort of issue, specifically the issue James Maltese has.
OS: Win 8 64 bit Pro
Motherboard: DZ77GA-70K.
Memory: Corsair. DDR3. 4GB x 2 . CML8GX3M2A1600C9B . I use "the 9-9-9-24 as suggested in the XMP profile"
Like James, I load the xmp memory profile in the BIOS and it shows 1600 Mhz. Once in windows the memory speed is reported as 1333 Mhz, both in the Intel Desktop Tool and in windows task manager.
At the risk of introducing a separate issue: I also sporadically get a 3 beep code (which designates a memory fault) and a failure to boot. I can rectify this by turning the power supply switch off then on. I can then boot as normal. This issue seems to arise regardless of whether I have set the memory speed at 1333 Mhz (auto memory profile) or 1600 Mhz (xmp memory profile). James (Jimmy), or anyone else, do you experience this?
I have run memtest86+ and the memory completes a pass with no errors.
Edit 1: BIOS Version 0059: GAZ7711H.86A.0059.2012.1106.1053. There is a newer BIOS version out, 0060, but nothing in the release notes to indicate these issues have been addressed.
Edit 2: When I get the 3 beep code I also get a Status Code of "20": "Resuming from [S2] State"