Code:
java.lang.NullPointerException
at forestry.arboriculture.items.ItemGermlingGE.getIconIndex(ItemGermlingGE.java:112)
at bce.a(RenderItem.java:130)
at cpw.mods.ironchest.client.TileEntityIronChestRenderer.render(TileEntityIronChestRenderer.java:180)
at cpw.mods.ironchest.client.TileEntityIronChestRenderer.a(TileEntityIronChestRenderer.java:191)
at bdw.a(SourceFile:103)
at bdw.a(SourceFile:96)
at bav.a(RenderGlobal.java:499)
at ban.a(EntityRenderer.java:1131)
at ban.b(EntityRenderer.java:974)
at net.minecraft.client.Minecraft.J(Minecraft.java:882)
at net.minecraft.client.Minecraft.run(Minecraft.java:771)
at java.lang.Thread.run(Unknown Source)
Delete your player.dat file from your server/world. Keep in mind you will lose your inventory and will move you to the serverspawn but atleast you should be able to login again.
Will test that on my testserver to see if i can replaicate it cause that whould be a nasty bug, can you remember what seeds or where it just normal seeds?