Wifi detected but doesn't work

HELP!

My good old Macbook Pro stopped working online. Every other device works with my DSL wireless modem/router (iPhones, Wii, Satellite receiver, iPad). The diagnostics tell me the Internet and Server failed.

I tried to go direct with an Ethernet cable with the same results.

I think the problem started when I allowed Firefox to upgrade Mozilla yesterday. I tried to delete the browser, library files, reset the PRAM, adjust modem/router settings. Something is still wrong, but strangely I was able to connect to update to Apple to update my software (under Apple menu)....

DSL- AT&T

Router- 2Wire 2701HG-B

Can anybody my old faithful machine? I was hoping to last a little longer before retirement.

Thank you in advance,

Mike