Object reference not set to an instance of an object.

Here is the stack trace... Happened on another devs machine randomly too.

[NullReferenceException: Object reference not set to an instance of an object.]
Cassette.BundleProcessing.CompileAsset.AddRawFileReferenceForEachImportedFile(IAsset asset, CompileResult compileResult) +29
Cassette.BundleProcessing.<>c__DisplayClass1.b__0() +88
Cassette.Stylesheets.<>c__DisplayClass3.b__0() +41
Cassette.Stylesheets.<>c__DisplayClass3.b__0() +41
Cassette.Stylesheets.ExpandCssUrlsAssetTransformer.ReadCss(Func`1 openSourceStream) +47
Cassette.Stylesheets.<>c__DisplayClass1.b__0() +38
Cassette.AssetBase.OpenStream() +103
Cassette.BundleProcessing.ConcatenatedStreamBuilder.Visit(IAsset asset) +33
Cassette.FileAsset.Accept(IBundleVisitor visitor) +10
Cassette.Bundle.Accept(IBundleVisitor visitor) +113
Cassette.BundleProcessing.AssignHash.Process(Bundle bundle) +79
Cassette.BundleProcessing.BundlePipeline`1.Process(T bundle) +93
Cassette.Stylesheets.StylesheetBundle.ProcessCore(CassetteSettings settings) +13
Cassette.Bundle.Process(CassetteSettings settings) +21
Cassette.BundleCollection.Process() +104
Cassette.BundleCollectionInitializer.Initialize(BundleCollection bundleCollection) +88
Cassette.RuntimeBundleCollectionInitializer.Initialize(BundleCollection bundles) +22
Cassette.ExceptionCatchingBundleCollectionInitializer.Initialize(BundleCollection bundleCollection) +34

[Exception: Bundle collection rebuild failed. See inner exception for details.]
Cassette.BundleCollection.GetReadLock() +374
Cassette.ReferenceBuilder.Reference(String path, String location) +67
Cassette.Views.BundlesHelper.Reference(String assetPathOrBundlePathOrUrl, String pageLocation) +29
Cassette.Views.Bundles.Reference(String assetPathOrBundlePathOrUrl) +18
ASP._Page_Views_Shared__Layout_cshtml.Execute() in c:\Code\Windsor\mi-miwaters-client-net\src\MiWaters\Views\Shared_Layout.cshtml:3
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +103
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +88
System.Web.WebPages.<>c__DisplayClass7.b__6(TextWriter writer) +233
System.Web.WebPages.HelperResult.WriteTo(TextWriter writer) +10
System.Web.WebPages.WebPageBase.Write(HelperResult result) +71
System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body) +64
System.Web.WebPages.WebPageBase.PopContext() +246
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +95
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +291
System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13
System.Web.Mvc.<>c__DisplayClass1a.b__17() +23
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +245
System.Web.Mvc.<>c__DisplayClass1c.b__19() +22
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +176
System.Web.Mvc.Async.<>c__DisplayClass2a.b__20() +75
System.Web.Mvc.Async.<>c__DisplayClass25.b__22(IAsyncResult asyncResult) +99
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +50
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
System.Web.Mvc.<>c__DisplayClass1d.b__18(IAsyncResult asyncResult) +14
System.Web.Mvc.Async.<>c__DisplayClass4.b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +39
System.Web.Mvc.Async.<>c__DisplayClass4.b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +29
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
System.Web.Mvc.<>c__DisplayClass8.b__3(IAsyncResult asyncResult) +25
System.Web.Mvc.Async.<>c__DisplayClass4.b__3(IAsyncResult ar) +23
System.Web.Mvc.Async.WrappedAsyncResult`1.End() +55
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +31
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9514928
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155