Asset has disappeared while building player

I write some code about build Ngui AssetBundle, but sometimes occur error

“Asset has disappeared while building player”

Asset has disappeared while building player:
UnityEditor.BuildPipeline:BuildAssetBundleInternal(Object, Object, String, String, BuildAssetBundleOptions, BuildTarget)
UnityEditor.BuildPipeline:BuildAssetBundle(Object, Object, String, BuildAssetBundleOptions, BuildTarget) (at C:\BuildAgent\work\7535de4ca26c26ac\Editor\MonoGenerated\Editor\BuildPipeline.cs:141)
BuildUtil:abBuild(String, Object, List1, BuildAssetBundleOptions, Int64, List1, List1, BuildTarget) (at Assets\Editor\BuldUtilities\BuildUtil.cs:185) BuildUtil:abBuild(String, List1, Int64, List1, List1, BuildAssetBundleOptions, BuildTarget) (at Assets\Editor\BuldUtilities\BuildUtil.cs:55)
BuildNGUI:doWork() (at Assets\Editor\BuldUtilities\BuildNGUI.cs:234)
ToolsPanel:Update() (at Assets\Editor\ToolsPanel.cs:290)

Textures 0.0 kb -1.% Meshes 0.0 kb -1.%
Animations 0.0 kb -1.% Sounds 0.0 kb -1.%
Shaders 0.0 kb -1.% Other Assets 0.0 kb -1.%
Levels 0.0 kb -1.% Scripts 0.0 kb -1.%
Included DLLs 0.0 kb -1.% File headers 0.0 kb -1.%
Complete size 0.0 kb -1.$%

and I found my Unity 4.1.2. doesn’t refresh automatically after modify csharp code, and I reboot computer and reinstall Unity, but it’s doesn’t refresh every time by modify code.

Same with our project