>The TextBox background colors appear OK until I make the form a Top Level Form. Once the top level form is running, just tabbing into the TextBox changes its background color. Tabbing out of the TextBoxes has random results. Sometimes they remain colored, sometimes they return to white.

Is there a Shape object involved anywhere? I had a similar problem a few years ago, which I still have a fix for if you need it (and problem is related to a shape).