When a Tcl/Tk program in Windows presents a tk_messageBox to the user and then, while the message box is active, the user switches to another open program, the message box remains on top of the Windows of the other program.
Alexandre Ferrieux reports that the problem resides in line 2183 of tkWinDialog.c, where the MB_SYSTEMMODAL flag was used rather than the MB_APPLMODAL flag.
RCS file: /cvsroot/tktoolkit/tk/win/tkWinDialog.c,v
retrieving revision 1.59
diff -r1.59 tkWinDialog.c
< flags |= icon | type | MB_SYSTEMMODAL;
> flags |= icon | type | MB_APPLMODAL;