I am not sure what your valence check error means, but some research indicates repairs have to be made while booted from the Recovery drive.
  1. Print these instructions.
  2. Power your computer down completely.
  3. Start your computer while pressing Command+R until you see the Apple logo.
  4. From the Recovery drive launch Disk Utility.
  5. Select your drive and click First-Aid
  6. Note the results.
  7. If errors are reported as not repaired, run First-Aid again.
  8. quit Disk Utility.
  9. quit Recovery Drive


If the DNS server is not working, you would not be able to use the internet. So whatever the error was, it was momentary. There are any number of open source DNS servers, Open DNS (the one Artie suggested) is among the very best and most reliable.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein