Minecraft crashes when chatting on MP server

I logged onto a MP server with factions plugin and switched to faction chat.
I then typed something into the chat and minecraft immediately crashed without freezing or locking up or giving any warning at all. I recieved this message on the 1.6.1 Minecraft launcher (I didn't read through it or add any thing, I just copy and pasted:

---- Minecraft Crash Report ----
// I blame Dinnerbone.

Time: 7/4/13 7:01 PM
Description: Deserializing Message

java.lang.ClassCastException: com.google.gson.JsonPrimitive cannot be cast to com.google.gson.JsonObject
	at cw.a(SourceFile:14)
	at cw.deserialize(SourceFile:10)
	at com.google.gson.TreeTypeAdapter.read(TreeTypeAdapter.java:58)
	at com.google.gson.Gson.fromJson(Gson.java:795)
	at com.google.gson.Gson.fromJson(Gson.java:761)
	at com.google.gson.Gson.fromJson(Gson.java:710)
	at com.google.gson.Gson.fromJson(Gson.java:682)
	at cu.c(SourceFile:220)
	at bcn.a(SourceFile:518)
	at dl.a(SourceFile:49)
	at cn.b(SourceFile:350)
	at bcn.d(SourceFile:95)
	at bcu.b(SourceFile:60)
	at atn.k(SourceFile:1380)
	at atn.S(SourceFile:662)
	at atn.d(SourceFile:618)
	at net.minecraft.client.main.Main.main(SourceFile:101)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at cw.a(SourceFile:14)
	at cw.deserialize(SourceFile:10)
	at com.google.gson.TreeTypeAdapter.read(TreeTypeAdapter.java:58)
	at com.google.gson.Gson.fromJson(Gson.java:795)
	at com.google.gson.Gson.fromJson(Gson.java:761)
	at com.google.gson.Gson.fromJson(Gson.java:710)
	at com.google.gson.Gson.fromJson(Gson.java:682)

-- Serialized Message --
Details:
	JSON string: Cannot send chat message.
Stacktrace:
	at cu.c(SourceFile:220)
	at bcn.a(SourceFile:518)
	at dl.a(SourceFile:49)
	at cn.b(SourceFile:350)
	at bcn.d(SourceFile:95)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bcx['Bfhead'/1010776, l='MpServer', x=60.56, y=156.62, z=13.29]]
	Chunk stats: MultiplayerChunkCache: 121
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (60,155,14), Chunk: (at 12,9,14 in 3,0; contains blocks 48,0,0 to 63,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 4966755 game time, 5093698 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
	Forced entities: 7 total; [rw['Sheep'/426740, l='MpServer', x=59.47, y=66.00, z=68.47], bcx['Bfhead'/1010776, l='MpServer', x=60.56, y=156.62, z=13.29], rn['Chicken'/307, l='MpServer', x=120.66, y=109.00, z=-32.72], rn['Chicken'/203, l='MpServer', x=79.38, y=68.00, z=72.63], ro['Cow'/179, l='MpServer', x=71.28, y=149.00, z=-8.69], ro['Cow'/227, l='MpServer', x=51.56, y=147.00, z=-41.50], ro['Cow'/226, l='MpServer', x=51.03, y=147.25, z=-40.13]]
	Retry entities: 0 total; []
Stacktrace:
	at bcu.a(SourceFile:284)
	at atn.k(SourceFile:1387)
	at atn.S(SourceFile:662)
	at atn.d(SourceFile:618)
	at net.minecraft.client.main.Main.main(SourceFile:101)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bcx['Bfhead'/1010776, l='MpServer', x=60.56, y=156.62, z=13.29]]
	Chunk stats: MultiplayerChunkCache: 121
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (60,155,14), Chunk: (at 12,9,14 in 3,0; contains blocks 48,0,0 to 63,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 4966755 game time, 5093698 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
	Forced entities: 7 total; [rw['Sheep'/426740, l='MpServer', x=59.47, y=66.00, z=68.47], bcx['Bfhead'/1010776, l='MpServer', x=60.56, y=156.62, z=13.29], rn['Chicken'/307, l='MpServer', x=120.66, y=109.00, z=-32.72], rn['Chicken'/203, l='MpServer', x=79.38, y=68.00, z=72.63], ro['Cow'/179, l='MpServer', x=71.28, y=149.00, z=-8.69], ro['Cow'/227, l='MpServer', x=51.56, y=147.00, z=-41.50], ro['Cow'/226, l='MpServer', x=51.03, y=147.25, z=-40.13]]
	Retry entities: 0 total; []

-- System Details --
Details:
	Minecraft Version: 1.6.1
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 19756064 bytes (18 MB) / 84758528 bytes (80 MB) up to 1037959168 bytes (989 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 5955 (333480 bytes; 0 MB) allocated, 92 (5152 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
	Launched Version: 1.6.1
	LWJGL: 2.9.0
	OpenGL: GeForce GTX 285/PCIe/SSE2/3DNOW! GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1594 (89264 bytes; 0 MB) allocated, 61 (3416 bytes; 0 MB) used