Like Sgt K indicated, try setting the channel setting in the router's administration section to something other than "auto" or "ch 6". If you have an android phone or tablet, download/install/run the WiFi Analyzer
. It will show the in use channels in your area which will allow you to find the least used channel.
If you are using an older Wireless G router, some were affected when you use a microwave or certain wireless phones. I had an older Linksys router that would dump all wireless connections when I turned on a microwave. Also check other electronic devices, its possible you are getting interference from other electronics. If the router is next to a computer or other electronics, move it at least 2 or more feet away from all electronics.
It might also be advisable to use a new router that supports Wireless N if your wireless clients support it. I have all my wireless clients tied to a separate Wireless N router that is connected to my 2Wire AT&T modem/wireless router. I had nothing but trouble with the 2Wire wireless signal with some of my devices.