Good tip, but this only solves not being able to connect at all (ever). Ever since one big patch (can't remember if it was cRPG or Warband), I couldn't connect to any servers until I did this. But it won't solve these momentary issues.
For instance, I had been playing in a couple of servers all afternoon, until I join EU_3 before a battle, and, when I'm rejoining, it said "unable to connect to the server". The only way I could fix it was to restart the game without WSE2, and restart again with WSE2. Then it worked.