welcome to the forums....
we need some more information....
1) what lights do you have on the cable modem at the moment?
2) what did technical support advise you about the issue? did they say it was a pc issue or what?
3) how long have you been having this problem?
4) where in the country are you?
5) usb or ethernet?
6) what version of windows?
7) you say you have only just got broadband, have you ever had it working since installation... has the cable modem been registered with the software?
8) what is your ip address?
(start > run > cmd or command > ipconfig)