{Alt+} shortcuts are used for menus. Pressing and holding alt activates the menubar area. This is standard Microsoft Windows behaviour. See

http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/keys_general.htm

(This is the online help for Windows 2000 Server but similar topics are presented in all versions since Windows 95)

>I have fixed this problem, but I want to know why it happens.
>

>Define myChkBox as ChkBox
>  Caption = 'Re\<fused'      && User can press {alt+f} to toggle value
>  Procedure When()
>    local lo
>    lo = Thisform.ActiveControl
>    This.Value = !This.Value
>    lo.SetFocus()
>    Return .F.
>  EndProd
>EndDefine
>

>This works just fine when the user clicks on the chkBox with the mouse, but if the user uses {alt+f} to do it, error "ACTIVECONTROL IS NOT AN OBJECT" and debugger shows "" for ActiveControl.
>
>Why does the keyboard shortcut throw away the ActiveControl?