I am getting the following error in the CMS admin area after performing an upgrade from 4.0.3 -> 4.5.2 -> 4.7.1.1.

Anyone have any ideas what's up? Thanks

Could not load type 'umbraco.controls.datePicker' from assembly 'cms, Version=1.0.4393.24040, Culture=neutral, PublicKeyToken=null'.

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.TypeLoadException: Could not load type 'umbraco.controls.datePicker' from assembly 'cms, Version=1.0.4393.24040, Culture=neutral, PublicKeyToken=null'.

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: 

[TypeLoadException: Could not load type 'umbraco.controls.datePicker' from assembly 'cms, Version=1.0.4393.24040, Culture=neutral, PublicKeyToken=null'.]

   PDCalendar.PDCalendarDataEditor..ctor(IData Data, String Configuration) +0

   PDCalendar.PDCalendarDataType.get_DataEditor() +175

   umbraco.controls.ContentControl.addControlNew(Property p, TabPage tp, String Caption) +93

   umbraco.controls.ContentControl.CreateChildControls() +609

   System.Web.UI.Control.EnsureChildControls() +102

   umbraco.controls.ContentControl.OnInit(EventArgs e) +32

   System.Web.UI.Control.InitRecursive(Control namingContainer) +140

   System.Web.UI.Control.AddedControl(Control control, Int32 index) +197

   System.Web.UI.ControlCollection.Add(Control child) +79

   umbraco.cms.presentation.editContent.OnInit(EventArgs e) +1169

   System.Web.UI.Control.InitRecursive(Control namingContainer) +140

   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +480