Loss of internet after 30 secs

Hi,

I have just come back from holiday and switched my pc on and have

found that everytime I connect to the internet I get disconnected

after 30 secs. I am connect to a cable modem and have spoken to the

provider and they inform me that everything is okay at their end. The

only way to get reconnected so that I can look at sites is to repair

the local connection but this again only allows me upto 30 secs

internet time. During this my local connection still shows me as

connected to my provider.

Can anyone please help?