The missing elements may shed some light on this picture, like fully listing your specs make and model#s, so we can see if there's a possible problem that doesn't have a thing to do with the actual overclock.
Like an underpowered system trying to push dual GPUs, or mismatched memory or wrong timings and such as that for example.
What you have enabled or disabled to reach this 4.5ghz overclock?
It's always a good idea to list your full specs first, then address the problem?
What test or tests you are actually running in Prime95?