Sounds very odd, I don't think overclocking is an ideal solution, esp with a retail system as the RAM probably wont take it (unless you can run a RAM divider).
When you say its capped... are you sure? runn a process in the background like prime95 then look and see what the speed is. it might just be that the CPU is being throttled down when not under load.
Intel core I7 920
6GB OCZ platinum 1600
Samsung 1TB F1 Spinpoint
Samsung SM2443BW 24"