When you overwrite the %Systemroot%\system32\drivers\etc\hosts file with a file that contains new entries, you may be unable to resolve a new hosts name entry?
You can ping the IP address address of the new hosts name entry, so connectivity is NOT the issue.
You can restart your computer to resolve this problem.
A better workaround is to open a CMD prompt and type ipconfig /flushdns.
You should receive a Successfully flushed the DNS Resolver Cache message.