Try going in 1.2.4, Turn your world to peaceful mode, then go to 1.2.5 and change it to normal mode see if that still happensMinecraft Crash Report:
i downloaded the 1.2.5 and it kept crashing, even after competly deleting and redownloading it
this is the Minecraft Crash Report i get from the FTB launcher.
full crash log uploadedMinecraft Crash Report ----
// Ooh. Shiny.
Time: 2/8/15 3:38 PM
Description: Exception in server tick loop
java.lang.UnsupportedClassVersionError: ASMAccessorImpl_7055204661423406299620 : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at org.mvel2.optimizers.dynamic.DynamicClassLoader.defineClassX(DynamicClassLoader.java:38)
at org.mvel2.optimizers.impl.asm.ASMAccessorOptimizer.loadClass(ASMAccessorOptimizer.java:2217)
at org.mvel2.optimizers.impl.asm.ASMAccessorOptimizer._initializeAccessor(ASMAccessorOptimizer.java:714)
at org.mvel2.optimizers.impl.asm.ASMAccessorOptimizer.optimizeCollection(ASMAccessorOptimizer.java:2986)
at org.mvel2.optimizers.dynamic.DynamicCollectionAccessor.optimize(DynamicCollectionAccessor.java:89)
at org.mvel2.optimizers.dynamic.DynamicCollectionAccessor.getValue(DynamicCollectionAccessor.java:66)
at org.mvel2.ast.InlineCollectionNode.getReducedValueAccelerated(InlineCollectionNode.java:82)
at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:42)
at org.mvel2.optimizers.impl.refl.nodes.MethodAccessor.executeAndCoerce(MethodAccessor.java:164)
at org.mvel2.optimizers.impl.refl.nodes.MethodAccessor.getValue(MethodAccessor.java:73)
at org.mvel2.optimizers.dynamic.DynamicGetAccessor.getValue(DynamicGetAccessor.java:79)
at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:108)
at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:38)
at org.mvel2.ast.Negation.getReducedValueAccelerated(Negation.java:48)
at org.mvel2.ast.Or.getReducedValueAccelerated(Or.java:34)
at org.mvel2.ast.Or.getReducedValueAccelerated(Or.java:34)
at org.mvel2.ast.Or.getReducedValueAccelerated(Or.java:34)
at org.mvel2.ast.Or.getReducedValueAccelerated(Or.java:34)
at org.mvel2.ast.Or.getReducedValueAccelerated(Or.java:34)
at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:42)
at org.mvel2.MVEL.executeExpression(MVEL.java:954)
at jas.common.helper.MVELHelper.typedExecuteExpression(MVELHelper.java:17)
at jas.common.helper.MVELHelper.executeExpression(MVELHelper.java:11)
at jas.spawner.modern.spawner.creature.type.CreatureType.canSpawnAtLocation(CreatureType.java:153)
at jas.spawner.modern.spawner.creature.type.CreatureType.canSpawnHere(CreatureType.java:242)
at jas.spawner.modern.spawner.CustomSpawner.spawnCreaturesInChunks(CustomSpawner.java:84)
at jas.spawner.modern.spawner.SpawnerTicker.performSpawningInWorld(SpawnerTicker.java:77)
at jas.spawner.modern.spawner.SpawnerTicker.serverTick(SpawnerTicker.java:46)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_1076_SpawnerTicker_serverTick_ServerTickEvent.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:138)
at cpw.mods.fml.common.FMLCommonHandler.onPreServerTick(FMLCommonHandler.java:260)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:536)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)