I would be considered an absolute novice at IT problems, yet there is a fault happening on my work computer that the IT experts here are not able to solve. I would appreciate any help you could offer for me to forward on to the IT Crowd...thanks.

DES v4.23.3 - An unexpected error has occurred in BTIS.TList at :
Int32 TTList.IsItemReallyVisible(TTList*, CTreeItem*) :
Object reference not set to an instance of an object.

Stack Trace : at TTList.IsItemReallyVisible(TTList* , CTreeItem* __unnamed000)
at TTList.GetLastVisibleBranchItem(TTList* , CTLTreeItem* pItem)
at TTList.GetPrevVisibleItem(TTList* , CTLTreeItem* pItem, Boolean bThis)
at TTList.ConvertTreeItemToVIndex(TTList* , CTreeItem* pTreeItem)
at TTList.T2V(TTList* , CTLTreeItem* pTreeItem)
at CTopView.WasFocusCellSet(CTopView* , CITLView* pITLView, SmartInterfaceEx<CTLTreeItem>* siLIItem, Int32* lVLIndex)
at CTreeView.Measure(CTreeView* , CMeasureData* rMData)
at CTLView.Measure(CTLView* , CMeasureData* rMData, Boolean bNotifyScrollbars)
at CTLView.Measure(CTLView* )
at CTLView.HitTest(CTLView* , CPoint* pt, CViewInfo* objViewInfo)
at TTList.OnMouseButtonUp(TTList* , CPoint __unnamed000, UInt16 fwKeys)
at BTIS.TList.TListWin.OnLButtonUp(MouseEventArgs e)
at BTIS.TList.TListWin.OnMouseUp(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at BTIS.TList.TListWin.WndProc(Message& msg)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

That error means one of the variables is not set to an object. It will be uninitialised instead. In your case this means that one of the variables in the line:
Int32 TTList.IsItemReallyVisible(TTList*, CTreeItem*) :
is not set to anything. You will need to check where these variables get their values in the previous code and find what is going wrong.

Can u try to give the exact code fragment that has a bug so we can help u out....The stack trace is not that helpful if u want to figure it out.

Hey dude

You can`t Properly created object for that instance.Please Check object properly created using new keyword like instances class, text box ,all controls