It is probably ur modem.
Here is something that might help
Intermittent loss of Internet connection
An intermittent loss of your connection to the Internet is often caused by electronic or physical interference.
* Cordless phones and other electronic devices are the most common cause of intermittent Internet connectivity issues. Cordless phone systems running at 2.4 GHz often run at the same frequency as your DSL modem or home networking router. If you are experiencing intermittent connectivity issues, you may need to replace your cordless phone with one that runs at a different frequency.
* Large metal objects and electrical equipment such as televisions, home entertainment electronics, and microwaves can also cause interference. Try to keep your DSL modem and wireless home networking router away from these sources of electronic interference.
* Check with your neighbor. You may both be running wireless networks at the same frequency. The solution may be as easy as changing the channel of your wireless router.
* Physical obstructions such as walls, floors, home entertainment electronics, appliances, and furniture can cause interference if the wireless signals have to pass through them. Move your DSL modem or wireless home networking router to another location so it isn't in the line-of-sight of these potential interference factors.
* Your phone jack may be defective or damaged. Try connecting the modem to a different phone jack, if possible. If the hiss and background noise is gone, the initial phone jack is defective and should be replaced.
* The RJ-11 phone cord that connects your modem to the phone jack may be damaged and need replacing. If your phone cord is over 14 feet long, the signal may be weakened sufficiently that it is intermittently lost.
* DSL filters are needed on all phone devices except the DSL modem. If you have more than one phone line entering your home, DSL filters should also be installed on the second line, even if it is not connected to your DSL equipment.
* The inside phone wiring in your home may also cause intermittent loss of the DSL signal. Shorts, grounds, poor line quality, etc. can degrade the DSL signal.
I hope this helps...
