Windows 7: Connection drop trouble

Hello everyone I'm from Brazil, and the new user forum.From two weeks down here have had problems in the fall of connection.I have two desktops: one in the living room and another in the bedroom is the first pc cable connection from the router connected to modem, and the room wirelles.The problem is that when the two are sailing in a game or even playing online or network connection that happens in the room drops,or the bedroom drop and get 2 pc without internet, only shortly after the connection back, and then drop again soon!
Already performed the following procedures and not getting success

1: reseted both [router = Siemens se361 =] and [modem motorola sbv5121]
2: updated the network drivers and device wirelles TP-Link wn-727n
3: formatted the 2 pc [both with windows 7 Home Premium x86]
4: I changed the channel on the router 1 ~ 11 and continued drop
5: I called my ISP and they said my connection was ok
6: I have 1mb speed.Already tried downloading and appears to be normal
7: When only one computer is online the connection does not drop

Sorry for my bad english.Any help is welcome.

No reply!thank you for nothing