Guys calm down.
That motherboard and CPU is still running within specs of AMD. It proberly does not have a over-current-protection that can be disabled so the danger is'nt as close as some might think. Newer boards are protected from high currents, they simply stall, reboot, crash but nothing serious.
Boards that do blow up have a bad VRM design, no protection or at least it triggers way too late.
Told you that playing with MP and FSB combined would archieve 4.4Ghz and above. The AMD cpu's have troubles doing higher mp's. You can actually force some more voltage into the PLL if i'm not mistaken so it stays stable, but oc'ing with FSB is always better then multiplier alone.
So, try to keep it stable now, and live with 4.4GHz. Or try 300Mhz HTT (FSB) which is more fun with a lower MP and memory dividers.
if you work with a Crosshair IV or even Formula-z you have a few options to raise the overcurrent, and disable the AMD recommendation for maximum usage of power of a CPU. This allows real hard OC'ing which can only be done on systems with proper cooling. Normal motherboards dont allow this and proberly 'limit' out on what the motherboard can deliver for a maximum.