DSL lost connections..does anybody know..

anything about what causes "Broadband Link Errors", saying I've lost DSL connection, when my router shows all lights on and connected, and computer shows a wireless connection, yet I lose link to Internet constantly??

AT&T router, 2Wire Gateway, about two-two1/2 years old.

Before I go buy a new router, would love to know I'm correct in doing that. AT&T troubleshooted all they knew to do for 90 min. phone call, didn't know what could be it.

Updated laptop Toshiba computer, i7, plenty or Ram etc, only 11/2 y.o., Windows 7, microsoft essentials security (formerly had Norton 360, still did this.)

Tks.