Cisco Linksys Wireless Router Loses Connection?

When ever my roommates and I turn on or turn off a computer or device to log onto our wireless network that computer or device and all other computers or devices that are on the network lose internet connection for about 3 minutes. After that period then all devices gain access back. We have a Cisco Linksys router, Model number WRT110, it is the Range Plus version. I got it 6 months ago from a friend that had never pulled it out of the box or used it. I used it before moving and it did not have this problem. We are using cable for our internet and have a Motorola Surfboard model number SB5101U for our Modem. We have 2 Dell computers, both about a year old, and a LG blue ray device that connects wirelessly to stream movies