I attempted to climb a ladder that I found in a NPC village and the ladder was taking up a whole block. You could not climb it. So I broke it to see if that would fix it. When I went to place the ladder the game crashed. This was in a pre 14w28a world. So I created a new world with 14w28a and the same thing happened. Second crash report is below.

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 7/9/14 12:08 PM
Description: Unexpected error

java.lang.IllegalArgumentException: Cannot get property bck

as it does not exist!
at bbw.b(SourceFile:91)
at avi.a(SourceFile:47)
at avi.a(SourceFile:35)
at apm.a(SourceFile:2320)
at ait.a(SourceFile:106)
at cdt.a(SourceFile:295)
at bqi.ar(SourceFile:1325)
at bqi.q(SourceFile:1682)
at bqi.ap(SourceFile:863)
at bqi.a(SourceFile:303)
at net.minecraft.client.main.Main.main(SourceFile:120)

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

– Head –
Stacktrace:
at bbw.b(SourceFile:91)
at avi.a(SourceFile:47)
at avi.a(SourceFile:35)
at apm.a(SourceFile:2320)
at ait.a(SourceFile:106)
at cdt.a(SourceFile:295)
at bqi.ar(SourceFile:1325)

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [chv['rudy30920'/125, l='MpServer', x=-73.43, y=75.00, z=266.29]]
Chunk stats: MultiplayerChunkCache: 289, 289
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: -64.00,64.00,256.00 - World: (-64,64,256), Chunk: (at 0,4,0 in -4,16; contains blocks -64,0,256 to -49,255,271), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 860 game time, 860 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: 50 total; [abn['Pig'/27, l='MpServer', x=-100.63, y=68.00, z=241.63], abn['Pig'/29, l='MpServer', x=-101.59, y=68.00, z=238.63], abn['Pig'/28, l='MpServer', x=-102.50, y=68.00, z=243.50], abf['Cow'/31, l='MpServer', x=-99.47, y=73.00, z=293.56], abn['Pig'/30, l='MpServer', x=-95.53, y=70.00, z=232.28], abf['Cow'/34, l='MpServer', x=-98.38, y=73.00, z=292.38], abf['Cow'/32, l='MpServer', x=-99.59, y=73.00, z=292.38], abf['Cow'/33, l='MpServer', x=-100.81, y=73.00, z=295.19], abn['Pig'/39, l='MpServer', x=-59.50, y=70.00, z=230.50], abn['Pig'/42, l='MpServer', x=-70.72, y=70.00, z=236.44], abn['Pig'/43, l='MpServer', x=-66.88, y=78.00, z=268.44], abn['Pig'/40, l='MpServer', x=-57.50, y=70.00, z=229.50], abn['Pig'/41, l='MpServer', x=-61.50, y=70.00, z=230.84], abn['Pig'/46, l='MpServer', x=-53.69, y=77.00, z=264.22], abn['Pig'/44, l='MpServer', x=-71.72, y=77.00, z=273.47], abn['Pig'/45, l='MpServer', x=-66.38, y=78.97, z=270.63], abn['Pig'/51, l='MpServer', x=-25.84, y=71.00, z=303.50], abn['Pig'/54, l='MpServer', x=-29.50, y=82.00, z=313.94], abn['Pig'/53, l='MpServer', x=-27.56, y=71.00, z=303.50], abn['Pig'/52, l='MpServer', x=-27.56, y=71.00, z=303.50], afk['Zombie'/10947, l='MpServer', x=-92.66, y=26.00, z=212.03], afk['Zombie'/17564, l='MpServer', x=-107.97, y=32.00, z=233.47], adr['Creeper'/17444, l='MpServer', x=-141.50, y=40.00, z=243.50], aex['Skeleton'/7372, l='MpServer', x=-17.50, y=59.00, z=239.50], adr['Creeper'/7369, l='MpServer', x=-19.50, y=59.00, z=239.50], adr['Creeper'/359, l='MpServer', x=-121.50, y=48.00, z=187.50], chv['rudy30920'/125, l='MpServer', x=-73.43, y=75.00, z=266.29], abb['Bat'/6177, l='MpServer', x=-87.63, y=24.09, z=201.53], adr['Creeper'/68461, l='MpServer', x=-8.50, y=30.02, z=286.50], aff['Spider'/50219, l='MpServer', x=-88.50, y=29.00, z=227.50], adr['Creeper'/68824, l='MpServer', x=-63.50, y=13.02, z=250.50], adr['Creeper'/11282, l='MpServer', x=7.50, y=57.00, z=230.50], afk['Zombie'/66757, l='MpServer', x=-114.50, y=26.00, z=200.50], afk['Zombie'/66758, l='MpServer', x=-114.50, y=26.00, z=202.50], afk['Zombie'/66755, l='MpServer', x=-119.50, y=26.00, z=204.50], adr['Creeper'/15629, l='MpServer', x=-144.50, y=39.00, z=222.50], adr['Creeper'/15628, l='MpServer', x=-141.22, y=43.00, z=220.88], afk['Zombie'/68612, l='MpServer', x=-18.50, y=44.02, z=295.50], afk['Zombie'/18421, l='MpServer', x=-100.97, y=41.00, z=205.50], aex['Skeleton'/68056, l='MpServer', x=-90.50, y=23.02, z=199.50], afk['Zombie'/68053, l='MpServer', x=-94.50, y=23.02, z=193.50], afk['Zombie'/68050, l='MpServer', x=-92.50, y=23.02, z=196.50], adr['Creeper'/67022, l='MpServer', x=-8.50, y=28.00, z=289.50], adr['Creeper'/67021, l='MpServer', x=-7.50, y=28.00, z=287.50], aex['Skeleton'/67027, l='MpServer', x=-8.50, y=28.00, z=287.50], adr['Creeper'/67907, l='MpServer', x=-34.50, y=51.02, z=265.50], adr['Creeper'/67906, l='MpServer', x=-35.50, y=51.02, z=263.50], afk['Zombie'/66978, l='MpServer', x=-34.50, y=56.00, z=309.50], afk['Zombie'/66979, l='MpServer', x=-34.50, y=56.00, z=311.50], afk['Zombie'/66980, l='MpServer', x=-30.56, y=55.00, z=305.94]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at cdu.a(SourceFile:308)
at bqi.b(SourceFile:2139)
at bqi.a(SourceFile:317)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 14w28a
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 93653160 bytes (89 MB) / 388939776 bytes (370 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Launched Version: 14w28a
LWJGL: 2.9.1
OpenGL: GeForce GT 520M/PCI/SSE2 GL version 4.1.0, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)