probably cos prime 95 is a tougher test than intel burn
try dropping it to 4.4ghz and see what happens not all 2500k will run 4.5ghz
is it important to pass prime 95 stress testing? as far as i am concerned if my overclock never blue screens or shuts down during heavy gaming -video encoding and running loads of programs at once then its stable
Your voltage is set awfully high, don't you think?
I agree with mcnumpty for the most part, if you can do everything that you normally do without BSOD, I'd say you're stable.
Although, it doesn't hurt to be able to pass Prime95 stress tests (more peace of mind I'd say).