i get this error message every time i type on a mp server:

---- Minecraft Crash Report ----
// I'm sorry, Dave.

Time: 7/9/13 4:21 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 bct.a(SourceFile:522)
at dl.a(SourceFile:49)
at cn.b(SourceFile:354)
at bct.e(SourceFile:98)
at bda.b(SourceFile:60)
at ats.k(SourceFile:1386)
at ats.S(SourceFile:663)
at ats.d(SourceFile:619)
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 bct.a(SourceFile:522)
at dl.a(SourceFile:49)
at cn.b(SourceFile:354)
at bct.e(SourceFile:98)

– Affected level –
Details:
Level name: MpServer
All players: 2 total; [bdf['Sideswpipe15'/1785048, l='MpServer', x=74.96, y=72.72, z=274.73], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75]]
Chunk stats: MultiplayerChunkCache: 169
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-132,71,332), Chunk: (at 12,4,12 in -9,20; contains blocks -144,0,320 to -129,255,335), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 824612661 game time, 825033033 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: 4 total; [bdf['Sideswpipe15'/1785048, l='MpServer', x=74.96, y=72.72, z=274.73], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75], bev['masterjbc'/1726495, l='MpServer', x=77.41, y=72.53, z=275.94]]
Retry entities: 0 total; []
Server brand: craftbukkit
Server type: Non-integrated multiplayer server
Stacktrace:
at bda.a(SourceFile:284)
at ats.k(SourceFile:1393)
at ats.S(SourceFile:663)
at ats.d(SourceFile:619)
at net.minecraft.client.main.Main.main(SourceFile:101)

– Affected level –
Details:
Level name: MpServer
All players: 2 total; [bdf['Sideswpipe15'/1785048, l='MpServer', x=74.96, y=72.72, z=274.73], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75]]
Chunk stats: MultiplayerChunkCache: 169
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-132,71,332), Chunk: (at 12,4,12 in -9,20; contains blocks -144,0,320 to -129,255,335), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 824612661 game time, 825033033 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: 4 total; [bdf['Sideswpipe15'/1785048, l='MpServer', x=74.96, y=72.72, z=274.73], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75], bev['masterjbc'/1726495, l='MpServer', x=120.63, y=71.00, z=275.75], bev['masterjbc'/1726495, l='MpServer', x=77.41, y=72.53, z=275.94]]
Retry entities: 0 total; []
Server brand: craftbukkit
Server type: Non-integrated multiplayer server

– System Details –
Details:
Minecraft Version: 1.6.2
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_21, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 35729296 bytes (34 MB) / 85577728 bytes (81 MB) up to 518979584 bytes (494 MB)
JVM Flags: 1 total; -Xmx512M
AABB Pool Size: 595 (33320 bytes; 0 MB) allocated, 21 (1176 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 3, tallocated: 63
Launched Version: 1.6.2
LWJGL: 2.9.0
OpenGL: GeForce 7025 / nForce 630a/integrated/SSE2/3DNOW! GL version 2.1.2, NVIDIA Corporation
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Pack: Rar$DRa0.303
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1032 (57792 bytes; 0 MB) allocated, 15 (840 bytes; 0 MB) used