Minecraft closes when I click at Multiplayer.

Hello dear players! When I click at the multiplayer, the game closes without leaving any message of crash. I find crash reports in the ''Crash Reports'' folder. This crash is only at the multiplayer, not at the singleplayer. I have Windows XP and Premium Minecraft. Please help me! I can't find solutions... :'(

Things I've already tried:

± Unistall Java and install it again.
± Unistall and install premium minecraft launcher again.
± Delete some folders from the .minecraft folder.
± Close many times my PC.