I have had a problem with the Multiple Uploader working on one of our sites and so I am trying to uninstall it so that I can start a fresh, however when I try to follow the instructions to remove the Multiple File Upload property from the folder Media Type I get the following error:

Server Error in '/' Application.
Object reference not set to an instance of an object.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.NullReferenceException: Object reference not set to an instance of an object.

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: 

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.cms.businesslogic.propertytype.PropertyType.delete() +77
   umbraco.controls.ContentTypeControlNew.gpw_Delete(Object sender, EventArgs e) +52
   umbraco.controls.GenericProperties.GenericPropertyWrapper.GenericPropertyWrapper_Delete(Object sender, EventArgs e) +28
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   umbraco.controls.GenericProperties.GenericProperty.DeleteButton2_Click(Object sender, ImageClickEventArgs e) +28
   System.Web.UI.WebControls.ImageButton.OnClick(ImageClickEventArgs e) +108
   System.Web.UI.WebControls.ImageButton.RaisePostBackEvent(String eventArgument) +118
   System.Web.UI.WebControls.ImageButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565








Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082

Alternatively, if anyone can help with the original error we have experienced that means I do not need to remove the property then that would be good.  Basically, when I click on a folder I get the following error:

Server Error in '/' Application.
The given key was not present in the dictionary.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.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.

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: 

[KeyNotFoundException: The given key was not present in the dictionary.]
   System.ThrowHelper.ThrowKeyNotFoundException() +28
   System.Collections.Generic.Dictionary`2.get_Item(TKey key) +2645040
   umbraco.cms.businesslogic.datatype.controls.Factory.GetNewObject(Guid DataEditorId) +41
   umbraco.cms.businesslogic.datatype.DataTypeDefinition.get_DataType() +101
   umbraco.cms.businesslogic.datatype.DataTypeDefinition.GetByDataTypeId(Guid DataTypeId) +41
   noerd.Umb.DataTypes.multipleFileUpload.MultipleFileUploadDataType.get_DataEditor() +61
   umbraco.controls.ContentControl.addControlNew(Property p, TabPage tp, String Caption) +87
   umbraco.controls.ContentControl..ctor(Content c, publishModes CanPublish, String Id) +783
   umbraco.cms.presentation.editMedia.OnInit(EventArgs e) +304
   System.Web.UI.Control.InitRecursive(Control namingContainer) +333
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +378








Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082

Any help would be appreciated.

Thanks

Paul