April 01, 2014 05:03 (11 months ago)
The same problem is going on with me.
I played yesterday for the first time, 5 hours straight. Then today I wake up and start the game, find that someone attacked my castle. I viewed the replay, and decided to better the defenses and then validated the castle. I then try to attack another castle, and it starts showing the same "network error" as you said. Restarted several times - the game, my pc, my router - but it doesn't work.
Hope you do something about it.
Here's the screenshot I took via steam.