Moving gnome-panel or start it in vertical position cause a crash in Openbox
(sometimes crashes entire XFree session).

System config:

Openbox-3.0-beta3
gnome-panel-2.2.2-1
XFree 4.3

Debian GNU/Linux Sid

Backtrace report:

(gdb) bt full
#0  0x40396ce1 in kill () from /lib/libc.so.6
No symbol table info available.
#1  0x402f8cc1 in pthread_kill () from /lib/libpthread.so.0
No symbol table info available.
#2  0x402f8f95 in raise () from /lib/libpthread.so.0
No symbol table info available.
#3  0x40396ac6 in raise () from /lib/libc.so.6
No symbol table info available.
#4  0x40397ced in abort () from /lib/libc.so.6
No symbol table info available.
#5  0x0806029a in sighandler (sig=6) at openbox/mainloop.c:346
        it = (GSList *) 0x402fdd38
        i = 0
#6  0x402fb98d in __pthread_sighandler () from /lib/libpthread.so.0
No symbol table info available.
#7  <signal handler called>
No symbol table info available.
#8  0x08068aa3 in screen_update_layout () at openbox/screen.c:728
        orient = OB_ORIENTATION_VERT
        corner = OB_CORNER_TOPLEFT
        rows = 0
        cols = 2
        data = (guint32 *) 0x810a7d0
        num = 4
        valid = 0
#9  0x0805aaf0 in event_process (ec=0xbffff8ec, data=0x0)
    at openbox/event.c:491
        window = 56
        group = (ObGroup *) 0x0
        client = (ObClient *) 0x0
        dock = (ObDock *) 0x0
        dockapp = (ObDockApp *) 0x0
	    x = 643, y = 984, x_root = 643, y_root = 984, mode = 0, detail = 2, 
    same_screen = 1, focus = 0, state = 0}, xfocus = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, window = 56, 
    mode = 288, detail = 93555}, xexpose = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, window = 56, x = 288, y = 93555, 
    width = 0, height = 643, count = 984}, xgraphicsexpose = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, drawable = 56, 
    x = 288, y = 93555, width = 0, height = 643, count = 984, 
    major_code = 643, minor_code = 984}, xnoexpose = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, drawable = 56, 
    major_code = 288, minor_code = 93555}, xvisibility = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, window = 56, 
    state = 288}, xcreatewindow = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, parent = 56, window = 288, x = 93555, y = 0, 
    width = 643, height = 984, border_width = 643, override_redirect = 984}, 
  xdestroywindow = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, event = 56, window = 288}, xunmap = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, event = 56, 
    window = 288, from_configure = 93555}, xmap = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, event = 56, window = 288, 
    override_redirect = 93555}, xmaprequest = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, parent = 56, window = 288}, 
  xreparent = {type = 28, serial = 5240, send_event = 0, display = 0x8098190,
        obwin = <value optimized out>
        ee = {type = 28, xany = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, window = 56}, xkey = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, window = 56, root = 288, 
    subwindow = 93555, time = 0, x = 643, y = 984, x_root = 643, y_root = 984, 
    state = 0, keycode = 2, same_screen = 1}, xbutton = {type = 28, 
    serial = 5240, send_event = 0, display = 0x8098190, window = 56,
    event = 56, window = 288, parent = 93555, x = 0, y = 643, 
    override_redirect = 984}, xconfigure = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, event = 56, window = 288, x = 93555, 
    y = 0, width = 643, height = 984, border_width = 643, above = 984, 
    override_redirect = 0}, xgravity = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, event = 56, window = 288, x = 93555, 
    y = 0}, xresizerequest = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, window = 56, width = 288, height = 93555}, 
  xconfigurerequest = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, parent = 56, window = 288, x = 93555, y = 0, 
    width = 643, height = 984, border_width = 643, above = 984, detail = 0, 
    value_mask = 2}, xcirculate = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, event = 56, window = 288, place = 93555}, 
  xcirculaterequest = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, parent = 56, window = 288, place = 93555}, 
  xproperty = {type = 28, serial = 5240, send_event = 0, display = 0x8098190, 
    window = 56, atom = 288, time = 93555, state = 0}, xselectionclear = {
    type = 28, serial = 5240, send_event = 0, display = 0x8098190, 
    window = 56, selection = 288, time = 93555}, xselectionrequest = {
    type = 28, serial = 5240, send_event = 0, display = 0x8098190, owner = 56, 
    requestor = 288, selection = 93555, target = 0, property = 643, 
    time = 984}, xselection = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, requestor = 56, selection = 288, target = 93555, 

    root = 288, subwindow = 93555, time = 0, x = 643, y = 984, x_root = 643, 
    y_root = 984, state = 0, button = 2, same_screen = 1}, xmotion = {
    type = 28, serial = 5240, send_event = 0, display = 0x8098190, 
    window = 56, root = 288, subwindow = 93555, time = 0, x = 643, y = 984, 
    x_root = 643, y_root = 984, state = 0, is_hint = 2 '\002', 
    same_screen = 1}, xcrossing = {type = 28, serial = 5240, send_event = 0, 
    display = 0x8098190, window = 56, root = 288, subwindow = 93555, time = 0, 
    property = 0, time = 643}, xcolormap = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, window = 56, colormap = 288, 
    new = 93555, state = 0}, xclient = {type = 28, serial = 5240, 
    send_event = 0, display = 0x8098190, window = 56, message_type = 288, 
    format = 93555, data = {
      b =
"\000\000\000\000\203\002\000\000