Horses Will Not Spawn at All

If you are unable to open the attachment, here is the crash report.

Minecraft Crash Report ----
// Why did you do that?

Time: 7/28/13 10:53 PM
Description: Manually triggered debug crash

java.lang.Throwable
at ats.k(SourceFile:1238)
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:
---------------------------------------------------------------------------------------

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [bdf['MylonJohnson'/426071, l='MpServer', x=-479.07, y=77.62, z=344.04]]
Chunk stats: MultiplayerChunkCache: 441
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (-168,64,240), Chunk: (at 8,4,0 in -11,15; contains blocks -176,0,240 to -161,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 338940 game time, 532639 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: 79 total; [ry['Sheep'/426091, l='MpServer', x=-521.91, y=69.00, z=306.97], tv['Zombie'/426092, l='MpServer', x=-515.50, y=14.00, z=330.50], tq['Skeleton'/426093, l='MpServer', x=-511.50, y=57.00, z=317.50], ry['Sheep'/426094, l='MpServer', x=-509.88, y=64.00, z=310.09], tv['Zombie'/426095, l='MpServer', x=-497.50, y=23.00, z=383.50], te['Creeper'/426080, l='MpServer', x=-552.50, y=42.00, z=360.50], tq['Skeleton'/426081, l='MpServer', x=-558.44, y=42.00, z=354.69], tq['Skeleton'/426082, l='MpServer', x=-554.09, y=40.00, z=356.50], ts['Spider'/426083, l='MpServer', x=-552.72, y=41.00, z=364.72], rp['Chicken'/426085, l='MpServer', x=-537.47, y=65.00, z=272.59], ry['Sheep'/426086, l='MpServer', x=-529.53, y=63.00, z=325.22], bdf['MylonJohnson'/426071, l='MpServer', x=-479.07, y=77.62, z=344.04], ry['Sheep'/426107, l='MpServer', x=-486.91, y=65.00, z=271.41], ry['Sheep'/426108, l='MpServer', x=-471.97, y=62.21, z=299.03], te['Creeper'/426232, l='MpServer', x=-556.50, y=31.00, z=270.50], tv['Zombie'/426099, l='MpServer', x=-492.50, y=26.00, z=385.50], tq['Skeleton'/426098, l='MpServer', x=-484.50, y=25.00, z=383.50], rn['Bat'/426100, l='MpServer', x=-489.66, y=24.36, z=389.31], te['Creeper'/426179, l='MpServer', x=-406.38, y=37.00, z=324.06], ts['Spider'/426178, l='MpServer', x=-401.72, y=36.00, z=308.97], ts['Spider'/426177, l='MpServer', x=-403.59, y=36.00, z=310.59], te['Creeper'/426176, l='MpServer', x=-407.50, y=36.00, z=315.50], tq['Skeleton'/426182, l='MpServer', x=-401.56, y=37.00, z=317.03], tq['Skeleton'/426181, l='MpServer', x=-403.50, y=36.00, z=314.50], te['Creeper'/426180, l='MpServer', x=-402.38, y=36.00, z=311.00], tv['Zombie'/426187, l='MpServer', x=-415.06, y=41.00, z=351.50], tv['Zombie'/426186, l='MpServer', x=-413.97, y=41.00, z=349.31], rn['Bat'/426188, l='MpServer', x=-403.56, y=41.10, z=351.59], tv['Zombie'/426075, l='MpServer', x=-543.69, y=13.00, z=327.91], te['Creeper'/426079, l='MpServer', x=-551.50, y=42.00, z=359.50], rp['Chicken'/426078, l='MpServer', x=-546.53, y=71.00, z=325.56], rp['Chicken'/426077, l='MpServer', x=-551.44, y=74.00, z=334.56], ry['Sheep'/426076, l='MpServer', x=-558.81, y=66.00, z=332.47], rn['Bat'/426149, l='MpServer', x=-430.47, y=39.10, z=282.25], rn['Bat'/426151, l='MpServer', x=-416.50, y=40.10, z=277.97], tv['Zombie'/426150, l='MpServer', x=-429.50, y=41.00, z=286.50], rn['Bat'/426145, l='MpServer', x=-450.78, y=35.32, z=424.41], rq['Cow'/426146, l='MpServer', x=-447.50, y=74.00, z=418.38], sb['Squid'/426157, l='MpServer', x=-426.22, y=51.34, z=378.50], sb['Squid'/426156, l='MpServer', x=-428.56, y=49.28, z=371.44], sb['Squid'/426159, l='MpServer', x=-420.09, y=51.81, z=369.66], sb['Squid'/426158, l='MpServer', x=-416.97, y=52.34, z=375.72], rn['Bat'/426153, l='MpServer', x=-426.25, y=39.10, z=289.25], st['entity.MinecartChest.name'/426152, l='MpServer', x=-419.50, y=41.50, z=289.47], st['entity.MinecartChest.name'/426155, l='MpServer', x=-427.50, y=40.50, z=359.50], sb['Squid'/426154, l='MpServer', x=-424.84, y=55.34, z=329.16], tv['Zombie'/426165, l='MpServer', x=-405.25, y=41.00, z=295.75], ts['Spider'/426166, l='MpServer', x=-406.56, y=41.00, z=295.34], sb['Squid'/426160, l='MpServer', x=-430.50, y=48.00, z=370.50], rn['Bat'/426161, l='MpServer', x=-426.59, y=24.57, z=418.53], rn['Bat'/426162, l='MpServer', x=-429.59, y=25.82, z=419.09], te['Creeper'/426172, l='MpServer', x=-413.09, y=36.00, z=307.72], te['Creeper'/426173, l='MpServer', x=-406.50, y=36.00, z=311.50], te['Creeper'/426174, l='MpServer', x=-406.50, y=36.00, z=315.50], te['Creeper'/426175, l='MpServer', x=-404.50, y=36.00, z=314.50], sb['Squid'/426168, l='MpServer', x=-416.50, y=59.28, z=290.25], st['entity.MinecartChest.name'/426169, l='MpServer', x=-410.50, y=37.50, z=304.09], te['Creeper'/426170, l='MpServer', x=-407.50, y=36.00, z=307.50], te['Creeper'/426171, l='MpServer', x=-409.50, y=36.00, z=306.50], tq['Skeleton'/426119, l='MpServer', x=-459.59, y=31.00, z=420.63], rn['Bat'/426118, l='MpServer', x=-453.75, y=30.10, z=416.34], tv['Zombie'/426117, l='MpServer', x=-456.47, y=31.00, z=420.94], tq['Skeleton'/426116, l='MpServer', x=-454.50, y=46.00, z=410.50], tv['Zombie'/426115, l='MpServer', x=-455.50, y=47.00, z=409.97], te['Creeper'/426114, l='MpServer', x=-448.50, y=15.00, z=404.50], te['Creeper'/426124, l='MpServer', x=-450.50, y=44.00, z=423.50], tv['Zombie'/426121, l='MpServer', x=-458.50, y=46.00, z=421.50], st['entity.MinecartChest.name'/426134, l='MpServer', x=-435.91, y=41.34, z=290.50], tq['Skeleton'/426135, l='MpServer', x=-438.63, y=41.00, z=292.22], te['Creeper'/426132, l='MpServer', x=-440.50, y=23.00, z=274.50], tv['Zombie'/426133, l='MpServer', x=-439.03, y=22.00, z=272.41], rn['Bat'/426130, l='MpServer', x=-434.50, y=38.10, z=270.88], tq['Skeleton'/426131, l='MpServer', x=-431.88, y=22.00, z=269.56], te['Creeper'/426128, l='MpServer', x=-436.66, y=22.00, z=271.31], te['Creeper'/426129, l='MpServer', x=-439.50, y=23.00, z=271.50], te['Creeper'/426138, l='MpServer', x=-445.56, y=36.00, z=308.03], st['entity.MinecartChest.name'/426139, l='MpServer', x=-443.50, y=22.34, z=341.50], tq['Skeleton'/426136, l='MpServer', x=-439.56, y=41.00, z=292.50], tq['Skeleton'/426137, l='MpServer', x=-437.50, y=41.00, z=293.00]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at bda.a(SourceFile:284)
at ats.b(SourceFile:1761)
at ats.d(SourceFile:628)
at net.minecraft.client.main.Main.main(SourceFile:101)

– System Details –
Details:
Minecraft Version: 1.6.2
Operating System: Mac OS X (x86_64) version 10.5.8
Java Version: 1.6.0_26, Apple Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
Memory: 215635320 bytes (205 MB) / 469884928 bytes (448 MB) up to 1069416448 bytes (1019 MB)
JVM Flags: 1 total; -Xmx1G
AABB Pool Size: 1145 (64120 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
Suspicious classes: No suspicious classes found.
IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
Launched Version: 1.6.2
LWJGL: 2.9.1
OpenGL: ATI Radeon X1600 OpenGL Engine GL version 2.0 ATI-1.5.48, ATI Technologies Inc.
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Pack: Default
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 2269 (127064 bytes; 0 MB) allocated, 18 (1008 bytes; 0 MB) used

Duplicate of MC-27153.
There you have the seed and coordinates of horses.