Ive got a problem with my brand new GT Chucker XS1-09 and its when im in the top 2 gears at the moment, if i put any pressure on the pedals the chain will jump around the cog's i was wondering what it could be

Lube it up, use Johnsons Baby Oil, always a good one.

but it looks as though its already lubed up pretty well

You can never have enough lube trust me

well Halfords gave me some of that GT stuff in the red can so i will put some of that on, if it carries on i'll take it in and see if it just needs a bit of adjusting

Yeah best thing to do is try that first, process of elimination, if that oil don't work try taking it down and getting it looked over just incase.

If it's brand new you should have some kind of warranty with it. Speak to the shop you bought it from, they should service the problem free of charge.

here is a good site for bikes.

http://bit.ly/nzLEQ

I had the same problem when I got my Cannondale F7 a few years back. I found out where to adjust the maximum and minimum distances that the derailleur can travel. It turned out that it was set to go far enough to hold strongly in 8th gear.

I had to do this again once the cables set in nicely. Lube also doesn't hurt at all.

Since then, I haven't really had a problem except going over strong bumps and accidentally shifting.

If its been assembled as a half arse job, then the derailleur probably won't even be configured correctly, so it'll just jump. If you know what you're doing, a few minutes with a screwdriver does the trick, or if you aren't comfortable doing that, just take it to a bike shop.

Also, if you're in the inner chainring and the outer cog, it'll make the chain so bent it'll hop back over. Try changing into the middle/outer ring and a middle cog.

well on the back ive got 8 cogs and the last one is tiny, on the front ive just got one big cog and it does seem the derailleur isnt adjusted properly because imo the chain is way too loose while in top gear

2 (edit, 3 actually) things:

1) If the chain jumps from one cog to another, then you have a misaligned derailleur.

2) If the chain "slips" as in you pedal and skip half a turn, your chain is loose. Go to some bike shop to have the chain fixed/replaced.

3) If the same thing happens as in 2), you could have some of the chain-links fused together by either insufficient lubrication or a simple defect. Lube those 2 links and make them "movable" again or go to your bike shop and have the chain fixed/replaced.

And sorry for using some weird terminology, but English is not my native language. I tried though, good luck.

These guys make a point. It would always be best to take it to a bike shop. If you're dealer is like mine, take it back to them if you can and see if they will service it for free or at a discount since you bought it there.

I get free life time service for bikes purchased at my local shop. I gotta take it in tomorrow as I'm missing a spoke, and the chain needs lubed.

EDIT___________

After oiling my chain today and noticing the result I'll say you should oil the chain first and see if that helps.