Internet works fine still cannot connect

I have an annoying issue with my internet connection. From time to time i can't connect to Steam, Battle.net or download from torrents (I'm mentioning torrents becuase there might be a connection). I share the internet with 10 other people all of them connected mostly via wi-fi. Is is possible that the connection is too low to connect to the already mentioned above servers? There is nothing wrong with my pc or internet settings because it works fine for a week and then all of a sudden not. Once we tried to hard reset the main router and after that it worked just fine.
Realy don't know what might be the reason and I would love to finally find out what's causing it.
The router is http://www.planet.com.tw/en/product/...t.php?id=34631
The modem is provided by austrian telecom company and is this one Pirelli PRG AV4202N

Thank you all for any help.