Macbook and ethernet issues

I have a bizarre situation. I access the internet at both work and home via ethernet.

My MacBook (OS10.5.8) has worked fine for years. The other day at home, it mysteriously

wouldn't access the internet. Gets online no problem with the connection at work. There's

nothing wrong with the home ethernet connection, as my ancient PC gets online.

So, we have active ethernet connections at two locales. Yet the MacBook only accesses the internet at work.

I was on the phone with an Apple tech last night, who could not solve the problem. Paid $19.95 for the privilege.

Any ideas at all?