Why does my CABLE Internet connection fail??
FIRST, UPDATE YOUR security program(antivirus, antispyware, firewall and so on).Next, check for viruses and spyware.If a malicious program turned your PC into Zombie, your internet link may overloaded with hidden, illegal activity.One infected PC can block access to your entire network.... 
After determining that your PC is free of malware, ping your connection to verify that the network hears you...
SELECT Start.Run, type command/k ipconfig AND press <Enter>
The resulting box shows your network seetings, one of which is your's PC's IP address.At the command prompt below these, type PING IPADDRESS, where ' ipaddress' is the number that follow ' IP Address.Press <enter>.You'll see a series of replies along with a list of ping statistics in millisecond.If the PING fails (''Destination host unreachable"), the problem is with your PC's network adapter, or the connection between the PC and the router. Type exit and press <enter>
to close the window.
One possible fix is to restart the router modem, or whatever device plugs first into the cable running from the wall.If the box lacks a power button, unplug it, wait a minutes, plug it back in, reboot your PCs, and see if the problem is gone.
If all of the computers on the network lose internet access simultaneously (and you've determined that malware isn't to blame), the problem is not with windows, the PC's hardware, your cable, or your's wi-Fi connection (if any).But if only one computer on the network loses access, the source of the problem could well be one of those compoonents.
If you use a WI-Fi network, check your wireless card's connection strength (most cards put an icon for this in the system tray).If the signal is weak, either remove obstructions (such as plants, fish tanks, or CD collections)from the signal path or move your PC closer to the wireless transmitter.
If all of your equipment is working, call your ISP's tech to support on-line troubleshoot.
Not easy to solve it
earn some incomes....is my interest to solve problem is not the $$$ concern...