You can stabilize a system by lessening the strain on the cpu by add more memory(ram). With more ram to work with, the frequency balance for your system (cpu, mobo, ram, hard disks) all perform better. So in matts case, he didn't have enough ram to have a stable overclock.
Dude Matt, I just finished building my beast whats your name and code on sc2?
ASUS P6X58D Premium
Intel i7 - 930 Bloomfield 2.8ghz
SAPPHIRE 100283L Radeon HD 5770 (Juniper XT) 1GB 128-bit GDDR5
G.SKILL 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)
First computer I built

ftw....