To reproduce:
-Set RTL via the insane:
RadMessageBox.Instance.RightToLeft = RightToLeft.Yes;

- You will notice that layout is not changed when the messagebox is shown.

Worlaround:
- Use the RadMessageBox show method with the following parameters:

RadMessageBox.Show(this, "test", "caption", MessageBoxButtons.OKCancel, icon, MessageBoxDefaultButton.Button1, RightToLeft.Yes);