Connection dropped?

My laptop works off the main computer via router. No problems until my husband just got a new computer. Now all of a sudden both of us are getting dropped connections.

Any idea where we should start? Would a bad router cause the main computer to get a dropped connection too? Both our connections are always dropped at the same time.

The only other connection is the DSL modem. Both computers are still hooked up, the old and the new. He's still transferring info.

Thanks so much!