You may be getting interference from neighbors using the sam channels you are on.
Use a utility such as inSSSIDer and look to see which channel is least used.
Then set your router to use this channel. Do not leave your router on automatic. Some devices get confused when the channel changes which could be part of the reason for your connection drops.
inSSIDer will only tell you how many people are using a channel but not how much. If the first channel you choose doesn't work.
If this doesn't help then the drops may be the result of a weak signal. If the devices that have the problem are several rooms away from your router you may need to add an AP to your network set up.
