Thank you for your reply.
Product: DIR-645 Firmware Version: 1.05 Hardware Version: A1
Purchased USA, used Europe. Correct channels.
Right now uses N+G, but thinking about it, I think I can make it N only.
Sure WPA2 + AES.
I understand wired is best, but it is very difficult adding wired LAN to the place of the client. 5GHz routers are quite scarce here and problematic to import, so I will have to wait with that for some time.
We don't put much on our network. Most of the time I can even choose Steam's highest quality settings – it reports about 25mbps used and estimates network speed at 100mb and it runs perfectly, but 2-3 times I tried turning on a laptop and it caused a freeze that kicked us out of the game. Afterwards, it is ok again. Turning off the laptop, there is a smaller interference. Another day it would have bad interference every few minutes. And that is all for medium quality, at about 15mbps.
Any further advice?