What happened is that you likely massively undervolted the cpu for a 4.8Ghz clock, haven't seen many 2600k that will do 4.6Ghz stably on 1.325v (and i mean stably, not 10 runs of ibt and 15mins prime), muchless 4.8. Try north of 1.35v, maybe 1.36v, likely you'll need more, i tend to stay under 1.4v but that just me, and you'll likely not (in my experience with 100+ 2600k thus far) achieve 4.8Ghz with that, a lot more don't than do.. Would use less DRAM voltage though, 1.5v is the spec for sandybridge, won't likely damage it but why risk it as your ram is likely 1.5v spec.