Android, Google: "Can't establish a reliable connection to the server"

Draft, ver. 1.0

127.201.26.224 android.clients.google.com mtalk.google.com

If you cannot add another Google account, getting errors:
Can't establish a reliable connection to the server
, or if synchronization of the existing Google services fails with:
Sync is currently experiencing problems
then your /etc/hosts file may be playing up.

Quite often this hosts file is created by an ad-blocking application, e.g. AdFree.

Despite this recommendation, it is not only this entry:
(see above)
that is playing up. In fact, I could not find it in my hosts file. I did not waste time experimenting which of these URLs is the right (wrong) one, so I just deleted the whole hosts file.

Here's how:
1. Run ES Explorer
2. Go to the root folder (/) and mount the system as Read/Write (now available in the Tools section, Root Explorer: ON)
3. Rename the /etc/hosts file to /etc/hosts.bak
4. Reboot (important).
5. Check if the hosts file is realy gone.
6. Try creating a new Google account again.

If that fails too, try toggling the connection between WiFi and Cellular. If all fails, try to restore the system from your restore point.