Try to look at the wireless network before and after the problem. If you right click on your wireless network and then click status, it should give you some information like radio (B,G,N,etc),band, channel, etc. What it says depends on your adapter and OS, but try to see what, if anything, changes after the disconnection, because thats probably what is causing your problem.
Most routers have auto-scan features and dynamic rates and a lot of other features that allow it to adjust to the wireless environment around it. I find a lot of routers will have problems informing the wireless clients of changes to the wireless network in real time, as the router adjusts. So if you have alot of neighbors around you with other wireless networks, your router may be adjusting itself, and each time it does, the wireless devices lose connection. Some of it is trial and error, but if you can find out what change is triggering the disconnection, it will help isolate the issue.