Ibanez RG 1750 Prestige is what I currently own i'm sure, not sure if its floyd rose or not but up at the neck theres 3 locks ?, ive lost the top lock for the top 2 strings but have the other 2 locks for the other 4 strings, however when I try to get the guitar in tune everythings just going out of tune now, any ideas how to sort this or do I need to get another lock ?
i think you mean RG1570? regardless, i know what you mean about the locks up on the neck i have them on my jackson. they're meant to keep the guitar in tune longer, called locking tuners.

although missing one will make those two strings come out of tune faster, they shouldn't go out of tune immediately after you tune them. many guitars don't have locking tuners, they're completely optional.

if they are coming out of tune immediately, i would check how secure the affected string are to the bridge and the neck. otherwise, take it in to be looked at. when i first got my jackson i had the exact same problem, and it ended up having to be exchanged for another of the same, because there was a bigger problem causing the strings to come out of tune.

you should still order another lock, not only for looks, but you don't want to be tuning those two strings twice as often as the others.

any questions reply or PM me.
cheers bud

what happens is i unscrew the bottem lock, tune it, screw it up, unscrew the second lock, tune it, screw it up then tune the top two, then i go do the fine tuners from bottem to top, and wen i play bottem, its back to the way it was before i started tuning =/ its crazy
Just information for you both, those aren't locking tuners, they're called locking nuts, locking tuners are tuners that have screws in them that hold the strings as opposed to wrapping it around the tuner and they help tuning stability.

You should definatley get another lock. So far as not being able to tune, thats really weird. I've dealt with quite a few floyd roses, and you can get pretty damn close to perfectly in tune before you even lock the nut. Ultimately you want the bridge parallel to the body of the guitar. if the strings always end up flat, then tighten the screws in the back of the gutiar, and if they always seem sharp, just loosen them. it takes a while but you should be able to get it. If not, take it in.