I will say this categorically, if any machine connects via to the web via the ntl connection it cannot be faulty, if you are using a router this is what the ntl connection negotiates via DHCP with, then the router assigns a private internal range of addresses which the router translates such that they can be actively routed over the internet.
So, it begs the question, is the the internet set up correctly on the linux box?
What IP address and subnet mask is in the configs? Is the linux box set up to negotiate DHCP?
Are you sure the gateway is set on the linux box?
Is the cable correct for the linux box?
Also please remember this is a non paid for forum written to by individuals who may be at work or elsewhere, they are not sitting there waiting to answer all questions instantly, so please, learn a bit of patience eh?
This site has proven itself (IMHO)to be friendly to everyone, that works both ways.
Now take a deep breath, and I would read the suggestions again from the top of this post, I think most of it made perfect sense and will help to define where the issue is.