Asus P8Z68-V-Pro-Gen3 Ethernet speed / Marvell problems

Hey Toms hardware!

Im quite new to the computer building scene, and have just built a new PC with the aid of a friend, who also helped me over clock my PC to around 4.7 Ghz.

However After updating my BIOS and other drivers to the latest from this website; I've encountered the following errors, Firstly when i boot my PC, sometimes it sticks on "Marvell Onboard Device Controller" or something similar, which will either then Load all normal and fine, or it will stick there, or it will load but not Detect my HDD, this seems random sometimes i boot once i've booted 10 times just to get it to Detect my HDD ( incase its relevant, my HDD is set to AHCL mode under BIOS and under the Marvel controls aswell. )

My 2nd problem is when my computer DOES boot, it will say "starting windows" and it takes quite a while for the windows logo to appear ( Win 7 64bit ), when it does appear and boot my internet speed will be around 50 kbs for some reason, i have fibre optic 50mb speeds, on my phone it runs fine, on the laptop aswell etc. but its just this computer that is having problems with it.

I am Running with an i5 2500k Overclocked to 4.7Ghz, 8Gb Kingston Hyper X ram, an EVGA Gtx 560, Asus p8z68-v-pro-gen3, and a corsair 850w PSU.

Not sure, but are you having similar problems?