Mine

Failed generating terrain map: System.ArgumentNullException: Argument cannot be null.
  at <0x00000> <unknown method>
  at (wrapper managed-to-native) System.Runtime.InteropServices.Marshal:copy_to_unmanaged (System.Array,int,intptr,int)
  at System.Runtime.InteropServices.Marshal.Copy (System.Byte[] source, Int32 startIndex, IntPtr destination, Int32 length) [0x00000]
  at OpenJPEGNet.OpenJPEG.Encode (System.Byte[] decoded, Int32 width, Int32 height, Int32 components, Boolean lossless) [0x00000]
  at OpenJPEGNet.OpenJPEG.EncodeFromImage (System.Drawing.Bitmap bitmap, Boolean lossless) [0x00000]
  at OpenSim.Region.Terrain.TerrainEngine.ExportJpegImage (System.String gradientmap) [0x00000]
[SCENE]         [09-23 09:49:06] Failed with exception System.NullReferenceException: Object reference not set to an instance of an object
  at OpenSim.Framework.Data.SQLite.SQLiteAssetData.UpdateAsset (OpenSim.Framework.Types.AssetBase asset) [0x00000]
  at OpenSim.Framework.Data.SQLite.SQLiteAssetData.CreateAsset (OpenSim.Framework.Types.AssetBase asset) [0x00000]
  at OpenSim.Framework.Communications.Caches.SQLAssetServer.CreateAsset (OpenSim.Framework.Types.AssetBase asset) [0x00000]
  at OpenSim.Framework.Communications.Caches.AssetCache.AddAsset (OpenSim.Framework.Types.AssetBase asset) [0x00000]
  at OpenSim.Region.Environment.Scenes.Scene.CreateTerrainTexture () [0x00000]
  at OpenSim.Region.Environment.Scenes.Scene.Update () [0x00000]
Failed generating terrain map: System.ArgumentNullException: Argument cannot be null.
  at <0x00000> <unknown method>
  at (wrapper managed-to-native) System.Runtime.InteropServices.Marshal:copy_to_unmanaged (System.Array,int,intptr,int)
  at System.Runtime.InteropServices.Marshal.Copy (System.Byte[] source, Int32 startIndex, IntPtr destination, Int32 length) [0x00000]
  at OpenJPEGNet.OpenJPEG.Encode (System.Byte[] decoded, Int32 width, Int32 height, Int32 components, Boolean lossless) [0x00000]
  at OpenJPEGNet.OpenJPEG.EncodeFromImage (System.Drawing.Bitmap bitmap, Boolean lossless) [0x00000]
  at OpenSim.Region.Terrain.TerrainEngine.ExportJpegImage (System.String gradientmap) [0x00000]
[SCENE]         [09-23 09:49:11]