Bug with binded properties of controls inside inactive tab

I try to make an Windows Forms application for .Net 2.0 with user settings.

1. I placed tabControl on a form.
2. I placed textbox control inside first tabPage, and another textbox inside second tabPage.
3. Binded first textbox.Text property to one Settings field, and second textbox.Text property to another field.

Now, when I run my app, the second settings field(tied to Text property of textbox inside inactive tab page) reads the default value, as it should be, but if I change text in first textbox, second textbox somehow "clears" at this moment, altering corresponding Settings field(makes it empty string). It stays "cleared" until I open the second 开发者_如何学Ctab, then it shows default value.

Described bug not happens, if I change text in first textbox after the second tab was opened.