Server key

Whenever i try logging on my minecraft says "Connection Lost The server responded with an invalid server key" i try reloading my minecraft but it doesn't work, the only way to fix it is to play singleplayer for a VERY long time and sometimes that doesn't even work. I know this happens to others too and i need help, what am i supposed to do when that happens?

When this happens, just simply:
- click "Back to title screen"
....wait 5 seconds (or you will get communication error)
- then click multiplayer and connect to the server.

Retry these steps until you finally get in, usually takes 2-5 times.

for me I normally have to close and reopen minecraft a few times before it lets me connect again. That's why when I log on I stay on for so long cause I don't wanna log out and have to go through the trouble of coming back in.