ERROR_ALREADY_EXISTS

Simple unity build: 1 asset, imported from an OBJ file and the main camera. When I press Build, the following error occurs:

IOException: Win32 IO returned ERROR_ALREADY_EXISTS. Path: System.IO.File.Move (System.String sourceFileName, System.String destFileName) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.IO/File.cs:337) PostProcessWinRT.RunSerializationWeaver () (at C:/buildslave/unity/build/PlatformDependent/WinRT/SharedSources/CSharp/PostProcessWinRT.cs:471) PostProcessWinRT.Process () (at C:/buildslave/unity/build/PlatformDependent/WinRT/SharedSources/CSharp/PostProcessWinRT.cs:123) UnityEditor.Metro.BuildPostprocessor.PostProcess (BuildPostProcessArgs args) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/ExtensionModule.cs:130) UnityEditor.PostprocessBuildPlayer.Postprocess (BuildTarget target, System.String installPath, System.String companyName, System.String productName, Int32 width, Int32 height, System.String downloadWebplayerUrl, System.String manualDownloadWebplayerUrl, BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.BuildReporting.BuildReport report) (at C:/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:176) UnityEditor.HostView:OnGUI()

Since I have no code, this is happening on the Unity side of things - unless it has something to do with the asset import. In any case, how do I solve this issue?