That is why.
3 problems there:
First being, you said your RAM is 1333. You need to make it run at 1333 or lower.
Second, your CPU has an FSB of 1333 and even though it is capable of running higher RAM speeds your RAM is pretty much limited to 1333 only.
Third, when you raise the FSB to overclock the CPU it raises the RAM speed too. You need to lower the RAM speed to something lower like 1066 so when you raise the FSB your RAM does not exceed 1333.
1.3v for that CPU should get you somewhere around 3.2-3.4GHz. Lower your RAM speed when you overclock the CPU and see if that helps.