This is the reply I recieved from Kingston...
Hello Mark,
Please check your processors documentation as it must be capable of also supporting 1066MHz memory. Here are the timings for the memory. If these don't work then sorry to say it's not compatible with your system even though you may have a processor that supports 1066MHz memory.
SPD Loads 800MHz
5 Cas Latency (CL)
5 Ras to Cas Delay or Row to Column Delay (tRCD)
5 Row Precharge Delay or Ras Precharge Delay (trp or tRCP)
15 Row Active Delay or Ras Active to Precharge Delay or Time to Ready (tra, trd or tRAS)
1 Command Rate (CMD) Please note not all bios will have this setting
1.8 Voltage
Module Max 1066MHz
5 Cas Latency (CL)
5 Ras to Cas Delay or Row to Column Delay (tRCD)
5 Row Precharge Delay or Ras Precharge Delay (trp or tRCP)
15 Row Active Delay or Ras Active to Precharge Delay or Time to Ready (tra, trd or tRAS)
1 Command Rate (CMD) Please note not all bios will have this setting
2.2 Voltage
SPD Loads are the default timings and how the module will run when it is simply plugged in the motherboard and turned on.
Module Max is the maximum settings the module can be overclocked to via BIOS settings.
Any other setting not listed here must be left to their default positions. If this memory does not run properly after setting the timings, please return the memory to the place of purchase within their return policy for a refund as they may not be compatible with your motherboard. You may also wish to obtain our conventional DDR memory not geared for overclocking by using our online memory configurator at:
http://www.ec.kingston.com/ecom/configurator_new/mfrmod.asp?root=us&LinkBack=http://www.kingston.com
Standard Memory: 0
MB (Removable)
Maximum Memory: 8
GB with current Kingston modules
16
GB with release of 4GB modules
Expansion: 4 Sockets
CPU & ChipSet: AMD Athlon 64 (AM2) AMD 790FX
AMD Athlon 64 FX (AM2) AMD 790FX
AMD Athlon 64 X2 (AM2) AMD 790FX
AMD Sempron (AM2) AMD 790FX
AMD Phenom FX (AM2+) AMD 790FX
AMD Phenom (AM2+) AMD 790FX
Bus Architecture: PCI;
PCI Express;
USB
Mfgr's System P/N's: N/A
Comments
DDR2-1066 is supported by AM2+ CPUs only.
At 1066MHz, this system supports up to two single rank modules ONLY.
MODULES MUST BE ORDERED AND INSTALLED IN PAIRS for Dual Channel mode. Kingston offers "K2"
Kit part numbers for Dual Channel mode.
AMD Sempron processors support DDR2-533 and DDR2-667 memory only. Faster speeds are not supported.
This system supports both
ECC and non-ECC memory. Mixing
ECC and non-ECC modules is not recommended.
If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation).
Maximum configurations require a 64-bit operating system.