two computers on lan problem

me and my brother have been playing cs/tf2 with eachother for months and it sometime after we got our new router we've been having problems playing in the same server. most of the time its fine with no problem but randomly when we try to connect to eachother we BOTH lag out of the server, our internet is still fine but the server lags out for both of us in both games.

how do i fix it so we can play in the same server?

Do you have a Emule or a torrent turned on ? Dunno but if everything is nicely configurated (most routers already come usable out-of.the.box) its probably a "bad" router problem. Ofc it really needs to be weak so it lags with only 2 clients. Check the DMZ of your router, and put one of your Pcs there. If the PC that is in the DMZ never crashes, you got there a Firewall/Config prob. This is more speculation, cause i really cant say what the prob is without more Info.

Try another router then. Its hard enough to by the phone, impossible in a forum post mate.