Thanks for the reply.  
I am with blueyonder/telewest.  I have a motorola surfboard modem which was supplied by Telewest.  I currently have to use a USB cable connected to the modem in order to connect to the internet (other end connected to PC).  The modem usually works ok when connected to the PC with a USB cable, but there has been a few occasions where I have had a system message saying limited or no connectivity, and have not been able to access the internet.  On these occasions, I have called Telewest, whose advice was to disconnect the power from the modem, wait a few minutes then reconnect the power to rectify the problem.  
When trying to use an ethernet cable to connect to the internet instead of the USB,there is ALWAYS an system/error message saying that there is limited or no connectivity.  I have then turned the modem off and on as directed by Telewest, and this has fixed the problem only temporarily.  
I managed to get enough of a signal to set up the router correctly, and now my PC detects the router, and appears to be connected to it, yet I can still not view any webpages.  Thus in order to connect to the net I have to be connected to the modem via USB.  I'm beginning to think that the problem may lie completely with the modem - what do you think?
                
 Sian
                
 September 2006