MSCRM 2011 - [FormatException: String was not recognized as a valid DateTime.] Lead Create/Update

Exception of type 'System.Web.HttpUnhandledException' was thrown.

[FormatException: String was not recognized as a valid DateTime.]
   at System.DateTimeParse.Parse(String s, DateTimeFormatInfo dtfi, DateTimeStyles styles)
   at Microsoft.Crm.Application.Platform.AttributeCollection.CreateValueFromDateTimePropertyValue(String name, Object value)
   at Microsoft.Crm.Application.Platform.AttributeCollection.SetEntityProperty(Entity entity, String name, String childAttributeName, Object parentProperty, AttributeMetadata attributeMetadata, Object value, IOrganizationContext context)
   at Microsoft.Crm.Application.Platform.AttributeCollection.Insert(String name, Object value, Boolean throwIfKeyExists)
   at Microsoft.Crm.Application.Platform.EntityProxy.SetData(XmlNode entityElement)
   at Microsoft.Crm.Application.Forms.EndUserForm.RetrieveParametersForEventDefault()
   at Microsoft.Crm.Application.Forms.EndUserForm.Initialize(Entity entity)
   at Microsoft.Crm.Application.Forms.CustomizableForm.Execute(Entity entity, FormDescriptor fd)
   at Microsoft.Crm.Application.Components.PageHandlers.LeadRecordPageHandler.ConfigureFormHandler()
   at Microsoft.Crm.Application.Components.Utility.GenericEventProcessor.RaiseEvent(String eventName)
   at Microsoft.Crm.Application.Controls.PageManager.OnPreRender(EventArgs e)
   at System.Web.UI.Control.PreRenderRecursiveInternal()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
[HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown.]
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest()
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Any help or Suggestions are appreciated.

Regards,