Lost Internet Connection

Lately I have problems getting onto the internet. This happens several times during the day. It only happens when I am getting onto the internet, not while I am on the net. Nothing has changed(hardware, software, disconnected cables etc) I use a Linksys cable modem. To get on the internet I have to unplug the modem and then plug it back in. After a few seconds my modem indicates I can connect to the internet. Why am I having these problems recently?

PS: I am still using Windows XP.