The documentation for the Asus Rampage IV Extreme gives no indication on the supported memory vendors list that it supports 8 sticks of memory or 32GB of RAM. Having said that, they tend to lie, my Asus P5E3 "supports 8GB' but runs just fine with 16GB of DDR3-1600.
Ensure your BIOS is updated to the latest version as this will have a significant impact on your RAM compatibility. You should be at BIOS 3301. If you're at 1404 or less then you will have run the BIOS converter first.
Their specs are:
8 x DIMM, Max. 64GB, DDR3 2400(O.C.)/2133(O.C.)/1866/1600/1333/1066 MHz Non-ECC, Un-buffered Memory
Quad Channel Memory Architecture
Supports Intel® Extreme Memory Profile (XMP)
* Hyper DIMM support is subject to the physical characteristics of individual CPUs.
* Refer to www.asus.com or user manual for the Memory QVL (Qualified Vendors Lists).
Make sure you turn on BIOS XMP support.