If you think you have wifi issues, check that it's not just Safari being broken first. Symptoms: Will load first web page, and then refuse to load subsequent pages.
Gross fix:
Terminal > curl -O https://dl.google.com/chrome/mac/stable/GGRO/googlechrome.dmg

Gross fix:
Terminal > curl -O https://dl.google.com/chrome/mac/stable/GGRO/googlechrome.dmg