Variable not found when package executes.".The element cannot be found in a collection."

Question

This is a very simple tutorial demonstrating script task. 2 variables
intvar int32 5
strvar string 0
And a script task with this code
If Dts.Variables("intVar").Value > 10 Then
            Dts.Variables("strVar").Value = "Big"
        Else
            Dts.Variables("strVar").Value = "Small"
        End If
        MsgBox(Dts.Variables("strVar").Value)
below is the error msg
SSIS package "Package.dtsx" starting.
Error: 0x1 at Script Task: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> Microsoft.SqlServer.Dts.Runtime.DtsRuntimeException: The element cannot be found in a collection. This error happens when
you try to retrieve an element from a collection on a container during execution of the package and the element is not there.
 ---> System.Runtime.InteropServices.COMException (0xC0010009): The element cannot be found in a collection. This error happens when you try to retrieve an element from a collection on a container during execution of the package and the element is not
there.
   at Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSVariables100.get_Item(Object Index)
   at Microsoft.SqlServer.Dts.Runtime.Variables.get_Item(Object index)
   --- End of inner exception stack trace ---
   at Microsoft.SqlServer.Dts.Runtime.Variables.get_Item(Object index)
   at ST_ce37649a37c146518fa69eff106c6625.vbproj.ScriptMain.Main()
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
   at Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTATaskScriptingEngine.ExecuteScript()
Task failed: Script Task
Warning: 0x80019002 at Package: SSIS Warning Code DTS_W_MAXIMUMERRORCOUNTREACHED.  The Execution method succeeded, but the number of errors raised (1) reached the maximum allowed (1); resulting in failure. This occurs when the number of errors reaches
the number specified in MaximumErrorCount. Change the MaximumErrorCount or fix the errors.
SSIS package "Package.dtsx" finished: Failure.
The program '[2824] Package.dtsx: DTS' has exited with code 0 (0x0).

Answer 1

Must be a typo in variable name (not matching declaration)
Arthur My Blog
there is one more reason for the problem - 
I had the code
DataColumn dc = null;
dc = myDataTable.Columns["PERSON_NAME"];
The column to be fetched was NAME and not PERSON_NAME...someone changed it in the db :(