Crashing

when ever I press the multiplayer button while i have minecraft in fullscreen mode it just crashes

---- Minecraft Crash Report ----
// Ouch. That hurt

Time: 2/9/14 9:52 AM
Description: Rendering screen

java.lang.IllegalArgumentException: bad Base64 input character at 6377: 0 (decimal)
at io.netty.handler.codec.base64.Base64.decode(Base64.java:247)
at io.netty.handler.codec.base64.Base64.decode(Base64.java:197)
at io.netty.handler.codec.base64.Base64.decode(Base64.java:188)
at bge.b(SourceFile:155)
at bge.a(SourceFile:130)
at bat.a(SourceFile:26)
at bay.b(SourceFile:382)
at bay.a(SourceFile:259)
at bgb.a(SourceFile:283)
at bll.b(SourceFile:851)
at azd.ad(SourceFile:780)
at azd.e(SourceFile:704)
at net.minecraft.client.main.Main.main(SourceFile:103)


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

-- Head --
Stacktrace:
at io.netty.handler.codec.base64.Base64.decode(Base64.java:247)
at io.netty.handler.codec.base64.Base64.decode(Base64.java:197)
at io.netty.handler.codec.base64.Base64.decode(Base64.java:188)
at bge.b(SourceFile:155)
at bge.a(SourceFile:130)
at bat.a(SourceFile:26)
at bay.b(SourceFile:382)
at bay.a(SourceFile:259)
at bgb.a(SourceFile:283)

-- Screen render details --
Details:
Screen name: bgb
Mouse location: Scaled: (406, 166). Absolute: (813, 379)
Screen size: Scaled: (680, 356). Absolute: (1360, 712). Scale factor of 2
Stacktrace:
at bll.b(SourceFile:851)
at azd.ad(SourceFile:780)
at azd.e(SourceFile:704)
at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
Minecraft Version: 1.7.2
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_45, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 30568560 bytes (29 MB) / 75546624 bytes (72 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.7.2
LWJGL: 2.9.0
OpenGL: GeForce 8300/integrated/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 Packs: [Coterie-Craft-v4s36.zip]
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~~ERROR~~ NullPointerException: null
Anisotropic Filtering: Off (1)