Getting my 1866Mhz memory to run at 1866Mhz on Alienware M18X R2

So, just a week ago I received my brand-new Alienware M18X R2.  When I placed the order, I asked for and received this memory:

1   319-1142    16GB,4X4G,1866MHz,DDR3

This isn't third-party stuff; it's one of the choices you get when you configure your Alienware.

However, the memory is only running at 1333Mhz.  I can go into the BIOS and set the speed to 1867, but it still only runs at 1333.  I must have rebooted fifty times trying various settings in the BIOS, and the memory only ever runs at 1333.

Finally, I figured it out.  There's something called the XMP Profile in BIOS.  You use it to set the memory timings so that it will run at a speed greater than 1333.  In fact, there's a preconfigured profile in the BIOS for 1866 Memory called "XMP Profile 2".

However, the BIOS refuses to use this profile.  In fact, it refuses to use *any* profile other than "Default".  If you choose another profile and "Save and Exit", it reverts the profile back to "Default".

Subsequent reading has uncovered the fact that this is *by design*.  Alienware doesn't want anyone "overclocking" their memory, so has locked out the overclocking functions in the BIOS.  Nevermind that I'm not overclocking my 1866 memory, I'm simply trying to get it to run at its designed specifications.

I don't understand why Dell would sell me 1866Mhz memory if it wasn't going to actually let me run it at 1866Mhz.

Is there anything that can be done?  I don't want to void my warranty by downloading an "unlocked" BIOS.