>The Lockscreen property value is set to .F. for the form.
Remember that properties may change at runtime. This may happen because you did it, or because your framework decided to do it. Check in the debugger, not only on the properties sheet.
Did you try my other idea - to do debugging, whether the Refresh() is actually called for one particular textbox?
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)