Computer fails to start with CPU at stock speed, but starts when less

So i just flashed my MB because i couldnt figure out what was causing this to happen and when i opened CPU-Z it showed it running at half speed (multiplier set to x7 instead of x15)! I went into the bios and changed it back to x15 but when my computer rebooted it got to the windows logo and rebooted, if I change it back to x7 it boots up just fine! Any answers would be amazing  



As you can see it is at 1.4GHz but it should be 3.0GHz  


Oops, I posted this late at night so I was extremely tired and forgot to put my specs, here they are.

CPU: AMD Phenom II 1075t, 6core, 3.0GHz
GPU: NVIDIA GeForce GTX 460, 768mb GDDR5
Memory: 4GB Kingston HyperX T1 (2x2), 1600 frequency
Motherboard: MSI 760GM-P35x
PSU: Corsair CX600, 600watt, +12V@40A