I've tried at least three times to install uBootstrap on a clean Umbraco 6.1.4 install. Each time, a few seconds into the install I get the following error and am left with an incomplete install. The only clean thing I am left to do is blow away my install and create another fresh install of Umbraco.

Server Error in '/' Application.
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 Specified cast is not valid. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidCastException: Specified cast is not valid.

Source Error: 




An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.


Stack Trace: 





[InvalidCastException: Specified cast is not valid.]
   umbraco.editorControls.datepicker.DateData.ToXMl(XmlDocument d) +87
   Umbraco.Core.Models.PropertyExtensions.ToXml(Property property, IDataTypeService dataTypeService) +368
   Umbraco.Core.Models.PropertyExtensions.ToXml(Property property) +38
   Umbraco.Core.Services.PackagingService.Export(IContentBase contentBase, String nodeName) +1262
   Umbraco.Core.Services.PackagingService.Export(IContent content, Boolean deep) +119
   Umbraco.Core.Models.ContentExtensions.ToXml(IContent content) +42
   Umbraco.Web.Search.ExamineEvents.IndexConent(IContent sender) +22
   Umbraco.Core.EnumerableExtensions.ForEach(IEnumerable`1 items, Action`1 action) +147
   Umbraco.Web.Search.ExamineEvents.ContentServiceSaved(IContentService sender, SaveEventArgs`1 e) +57
   Umbraco.Core.Events.EventExtensions.RaiseEvent(TypedEventHandler`2 eventHandler, TArgs args, TSender sender) +16
   Umbraco.Core.Services.ContentService.Save(IEnumerable`1 contents, Int32 userId, Boolean raiseEvents) +647
   Umbraco.Core.Services.PackagingService.ImportContent(XElement element, Int32 parentId, Int32 userId) +195
   umbraco.cms.businesslogic.packager.Installer.InstallBusinessLogic(Int32 packageId, String tempDir) +2575
   umbraco.presentation.developer.packages.Installer.ProcessInstall(String currentStep) +208
   umbraco.presentation.developer.packages.Installer.Page_Load(Object sender, EventArgs e) +435
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   umbraco.BasePages.BasePage.OnLoad(EventArgs e) +14
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207



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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272