Wireless Problem

[ste-sim2x9]

Me an the wife both have a laptop, i have a asus G73 and the wife has a acer aspire 6530G. I have mine connected via lan cable because i feel more comfortable at my desk and because of better speeds where as my wife sits on the sofa surfing the web wirelessly. For some reason her internet somtimes disconnects and does not reconnect, so i click on the wireless icon on the taskbar by the clock and my router is shown. So i click connect it says connecting then comes up with cannot connect to network. If i power down the laptop and power back on the laptop will reconnect. I was using a netgear wgt624 that i'd had for quite a while and it disconnected on that so i went out and brought a new router. I'm now using a Linksys WRT160NL router and have changed the wireless channel but still it disconnects. i've even installed DD-WRT firmware to see if that worked but it still disconnects. One stange thing i noticed yesterday was my wife said her laptop had diconnected again but at the time i had my friends laptop next to mine downloading updates wirelessly after i had to recover his system after a crash and that was still connected. Would that point to a problem with the wifes laptop or something else i've missed.