CheckedListBox problem with .net Framework4

We have a program developed with Vb.net which uses CheckedListBox control and the program is converted from VB6 to Vb.Net
"VB6.GetItemString" method is used to get the item value from CheckedListBox
With Frame work 3.5 or Framework 4 along with Frame work 3.5 "VB6.GetItemString" method works properly
But when Frame work 4 alone was installed the "VB6.GetItemString" property returned empty(Download link for Frame work 4 : http://www.microsoft.com/en-us/downl....aspx?id=17718)
Whether this feature is not supported by Frame work 4? Is there similar kind of such feature which are not supported by frame work 4?
Can somebody tell what is the solution for this?

Is the control actually a System.Windows.Forms.CheckedListBox? If so then just use the control's own GetItemText method.