In the following sample (with themes activated) I can't see the border to appear on mouse hovering anymore:
EMG
#include "Fivewin.ch"
FUNCTION MAIN()
LOCAL oDlg
DEFINE DIALOG oDlg
@ 2, 2 BTNBMP FILE "c:\fwh\bitmaps\open.bmp";
NOBORDER
ACTIVATE DIALOG oDlg;
CENTER
RETURN NILEMG