Since you mention leaving the modem off overnight I assume you have a cable modem. (Sorry but I have never heard of Blueyonder). Is your interface up?

Code:
ifconfig -a
Do you have an IP address?
If not, have you tried taking it down and bringing it back up?

Code:
su
<password>
ifdown -a
ifup -a
ifconfig
Got an IP address now? If so, can you ping? What tools have you used thus far?

No IP address yet?- Do you use DHCP? Do you normally have to log on to the Blueyonder network somehow? How is your modem connected to your pc? More details please.....