I would add try-catch blocks around the instruction(s) that manipulate your table:

local oException as Exception
try
      SELECT vProd
      REPLACE vProd.Due_Date1 WITH this.dDate
catch to oException when oException.errorNo = 114
     messageBox(Textmerge([Error 114 occurred at <<Datetime()>> on "REPLACE vProd.Due_Date1 WITH this.dDate"])) && or log to a file
endtry

>>>The problem is 3-4 times out of 10, when they increase or decrease the due date spinners, they get the error:
>>>"Error # 114: Index does not match"
>>
>>Do you have code in the 'due date spinners' event methods such as .InteractiveChange() and/or .Valid()?
>
>Thank you for your response;
>Yes I do.
>
>

>* Init() has:
>this.dField = 'vProd.Due_Date1'
>this.InitDate = DATE()
>DateSpinner::Init()
>this.Parent.lblDow1.Refresh()
>
>* Gotfocus() has:
>this.BackColor = p_bcs
>DODEFAULT()
>thisForm.lblHome.Visible = .T.
>thisForm.lblHome.Refresh()
>
>* InterActiveChange() has:
>DateSpinner::InterActiveChange()
>this.Parent.lblDow1.Refresh()
>
>* LostFocus() has:
>this.BackColor = p_bc
>DateSpinner::LostFocus()
>IF this.Parent.SpDue2.dDate < this.dDate
>   this.Parent.SpDue2.dDate = this.dDate
>   this.Parent.SpDue2.Refresh()
>ENDIF   
>DODEFAULT()
>thisForm.lblHome.Visible = .F.
>thisForm.lblHome.Refresh()
>
>Valid() has:
>IF DateSpinner::Valid()
>   this.Parent.lblDow1.Refresh()
>   IF vProd.Due_Date1 # this.dDate
>      SELECT vProd
>      REPLACE vProd.Due_Date1 WITH this.dDate
>   ENDIF   
>   RETURN .T.
>ENDIF   
>
>* Refresh() has:
>this.Enabled = thisForm.lAllowEdits .OR. thisform.HotLink
>DateSpinner::Refresh()
>this.Parent.lblDow1.Refresh()
>

>
>Thanks.