Issues with overclocked CPU

[Squish8294]

Using RAMCache, while prime95ing, on an overclocked i5-3570k (4.2 GHz, 1.240 VCore) will cause prime95 to return errors and fail self tests - overall PrimoCache is very stable that I've noticed, with exception to this. Overall I was downloading Battlefield 3 via Origin, running a skype call, using a 2048MB Ram Cache to a momentus XT hybrid drive from seagate, using prime95 as outlined above, monitoring temps on my CPU via corsairlink 2 (I have an H100i), watching my resource usage using task manager, keeping a load on nVidia based MSI Cyclone GTX 460 1GB edition overclocked to 800/1600/1850, 1.062v and lastly, messaging on steam.
System Specs:
MB: ASUS P8Z77-V LK
CPU: i5-3570k OC 4.2GHz all powersaving features off, VCore 1.240
RAM: 2x Kingston HyperX Black 1600MHz 8GB CAS timings 9-9-9-24 Voltage 1.5000V
HardDrive: Seagate Momentus XT Solid State Hybrid Drive 500GB/4GB nAND flash partition used as a read-only cache on LFU-R setting (Or equivalent set by drive firmware)
Graphics Card: MSI Cyclone GTX 460 1GB Ed.
Secondary (Storage) Hard Drive: Seagate FreeAgent GoFlex 2TB HDD on SATA 3.0Gbps port

Other:

PrimoCache settings had 2048 RAM Allocated to the Momentus using 4k blocks on Read/Write cache using LFU-R Defer write using 15 s latency, NO L2 cache.

[InquiringMind]

Squish8294,
If you've not already done so, it may be worth checking whether your memory is overclocked or not (changing BCLK on its own will usually increase memory frequency unless it is set to a specific value). PrimoCache will result in higher memory usage so could be raising memory temperatures compared with Prime95 alone.