I've recently bought a new motherboard the Asus P8 Z68-V Pro. I've been having problems with my computer, specifically screen flashing black and then back again and the computer doesn't turn on straight away.
I've noticed that my motherboard doesn't have a CLRTC jumper, is this needed? could this be causing problems?
As per your clarification that you simply mean the jumper is missing, to my knowledge on the majority of modern motherboards, this simply doesn't matter. The two pins that you bridge to trip the RTC clear are wired, but the third pin doesn't really do anything and is simply there so that the jumper can remain in the machine.
That said, for the issues you're having it couldn't hurt to reset the CMOS and then immediately do a clean flash of the newest BIOS revision and reset your settings from scratch. In the absence of a jumper, you can simply bridge the two pins for a few seconds with a screwdriver or pocketknife.
