Custom form fails when attachments are added to task

I have two public folders in exhange that use nearly identical custom Outlook 2010 forms. The differences are only that some of the peoples names used in vbscript variables are different. One form works fine. The other form crashes when a task (opened from the custom form via the code below) has an attachement added to it, and I try to save/close the task. There is no vba code, only vbscript.

Since the forms are basically identical, and the default form for the folders point to the correct forms, I can't figure out why it crashes. It used to report a script error like this:

Script Error

Object Required: 'MyServiceItemItems(...).Userproperties.find(...)' Line No:37

However since I added some code to try to solve this, it simply crashes outlook. Is line 37 a line in my custom vbscript code? Is the numbering relative to the entire page of code, or the line # inside the offending subroutine? There is no function MyServiceItemItems() but the form is called ServiceItem.

At an earlier stage I was getting this error msg:

One or more items in the folder you synchronized do not match. To resolve the conflicts, open the items, and then try this operation again. Line No: 37

I don't see any sync error messages in the folder. I'm assuming they'd be obvious.

I read somewhere that it might be necessary to rebuild this folder, but I'm not sure how to do that.

Can someone help me understand what might be going on and how to solve it?

Here is the code that opens the task (probably no issue here)

'*************************************************************************
'* Procedure:      PendingAction_Click
'* Description:     Opens a Task Form  in the user personal task folder
'*************************************************************************
Sub PendingAction_Click
    Item.Save
    NextTaskNo = Item.UserProperties.Find("TaskNo").Value + 1
    Set myNameSpace = Application.GetNameSpace("MAPI")
    Set AssignedFolder = myNameSpace.GetDefaultFolder (13) 'PersonalTasksFolder
    Set TaskItem = AssignedFolder.Items.Add("IPM.Task.SupportTask")
'    Set TaskItem = Application.CreateItem(3)
    TaskItem.Subject = Item.UserProperties.Find("CaseNo").Value & _
        " Task # " & NextTaskNo & " -- "
    TaskItem.UserProperties.Find("CaseNo").Value = _
        item.UserProperties.Find("CaseNo").Value
    TaskItem.UserProperties.Find("TaskNo").Value = NextTaskNo
    TaskItem.StartDate = Now()
    TaskItem.DueDate = Now () + 1
    TaskItem.ReminderSet = True
    TaskItem.BillingInformation = "New"
    TaskItem.Display
'    TaskItem.Attachments.Add Item,4
End Sub