Server Connection Error

I had a screen with only the normal background without any text by connecting to a server and after approximately 25 second that showed me that and it's not a IPv6 problem
Is that a probleme of connection ? I cannot reproduce the probleme (Because i forgot the IP server) ,I used a a DNS server for my server on the same desktop and i had the same error, I have an acceptable connection ( 8.07 Mb / s )
"I tink the server was Extremely slow"

Changes 1.5.2 : This time it dosn't crash but i can't go on the server =/

Unexpected error

java.lang.NullPointerException
at aww.a(SourceFile:57)
at ayt.b(SourceFile:755)
at net.minecraft.client.Minecraft.J(SourceFile:604)
at net.minecraft.client.Minecraft.run(SourceFile:534)
at java.lang.Thread.run(Unknown Source)

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