We have a small network of 3 PCs sharing the same BT Broadband connection through a Zyxel Prestige 642T-11 ADSL Router and a Corega Switching hub. We have started to experience problems connecting some of the PCs to the internet. The problem comes and goes and not all PC's are affected at the same time. The network has worked fine for a long time but something seems to have changed.

The fact that the problem comes and goes through the day is strange. All PC's can receive email even when the problem is occuring. Whilst we are unable to connect to most sites the ones we use regularly will often still let us in.

As I said the problem comes and goes. At other times all PCs can connect with no problems and can browse any site.

Does this sound like a problem with the Router, a virus, a BT broadband issue or something else?

All 3 PCS are W2K systems.

I am not overly technical so if we could keep it simple that would be appreciated. Any advice gratefully received.