[MC-2507] Entering IPv6 servers crashes the client

When i'm trying to add a IPv6 Server, i cant click on "save".
(Screenshot 1, mc1.png)

When i'm trying to connect directly to the IPv6, i get as response:
"java.net.SocketException: Protocol family unvailable"
(Screenshot 2, mc2.png)

Sometimes it crashes while trying to use IPv6:

---- Minecraft Crash Report ----
// Ooh. Shiny.

Time: 08.11.12 17:34
Description: 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)

Relevant Details:
- Minecraft Version: 1.4.2
- Operating System: Windows 8 (amd64) version 6.2
- Java Version: 1.7.0_09, Oracle Corporation
- Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
- Memory: 489391232 bytes (466 MB) / 524550144 bytes (500 MB) up to 954466304 bytes (910 MB)
- JVM Flags: 2 total; -Xms512m -Xmx1024m
- AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
- LWJGL: 2.4.2
- OpenGL: ATI Radeon HD 3870 X2 GL version 3.3.11653 Compatibility Profile Context, ATI Technologies Inc.
- Is Modded: Probably not
- Type: Client
- Texture Pack: Default
- Profiler Position: N/A (disabled)
- Vec3 Pool Size: ~ERROR~ NullPointerException: null