I get this problem when trying to join servers. I've tried many server IP's from http://minecraftservers.org/. All of them used to work, but after I downloaded the latest snapshot it won't. I've reset all my firewall settings to make sure of that, and my buffers are sett to 512 as some sugested. I've scrolled trough some sites looking for an answer but can't find anything. Help?
Okay my buddies figured it out for me. Here we go:
1.) google "minecraft snapshot week 25"
2.) Download the client .jar file.
3.) find your .minecraft file folder
4.) go into bin file
5.) drop new .jar in and move and replace this.
6.) log out and log back in.
I was on the same boat as all of you until I figured out the problem. If you have Java 7 on your computer delete it and downgrade to Java 6 update 13. I found out that for some reason Java 7 is not completely functional with Minecraft 1.2.5. Then once you able to update minecraft upgrade up to Java 7. That should solve your problem.
1.3.1 is now out and when i was playing in 1.2.5 the servers worked. Next thing i know when i log on it says a new update is avalable do you want to update. I say yes and it loads compleatly normally but when i try and get on servers it comes up with this error.
If anybody knows how to undo the update or how to fiz the problem that would be great.