Reproduced here:

The program 'firefox-bin' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 40107 error_code 8 request_code 155 minor_code 4)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

It looks like mozilla 304370 [1] (and others, query 'badmatch') which has a similar behaviour with adobe flash 7 or 9; they are claimed as flash bugs and not mozilla ones.
They also have a different error_code, request_code and minor_code. Not that i know what they mean though :)

Following the advice given on console should help. Sergio if you are willing to do that would be great :)

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=304370

I can reproduce this too, here is the backtrace (with --sync):

#0  IA__g_logv (log_domain=0x7fd909213c73 "Gdk", log_level=G_LOG_LEVEL_ERROR, format=0x7fd909231067 "%s", args1=0x7fff176c6960)
    at /build/buildd/glib2.0-2.17.6/glib/gmessages.c:503
#1  0x00007fd90a404fd3 in IA__g_log (log_domain=0x7fd90e8dfa00 "", log_level=0, format=0x2db0600 "ZZZ\231YYY\231�\001")
    at /build/buildd/glib2.0-2.17.6/glib/gmessages.c:517
#2  0x00007fd9091fbde2 in gdk_x_error (display=<value optimized out>, error=<value optimized out>) at /build/buildd/gtk+2.0-2.13.6/gdk/x11/gdkmain-x11.c:641
#3  0x00007fd909ef1864 in _XError (dpy=0x645e60, rep=0x2db00f0) at ../../src/XlibInt.c:2912
#4  0x00007fd909ef92df in process_responses (dpy=0x645e60, wait_for_first_event=0, current_error=0x7fff176c6c38, current_request=59899)
    at ../../src/xcb_io.c:138
#5  0x00007fd909ef968a in _XReply (dpy=0x645e60, rep=0x7fff176c6c80, extra=0, discard=1) at ../../src/xcb_io.c:370
#6  0x00007fd909eed0c3 in XSync (dpy=0x645e60, discard=0) at ../../src/Sync.c:48
#7  0x00007fd909eed27b in _XSyncFunction (dpy=0x7fd90e8dfa00) at ../../src/Synchro.c:37
#8  0x00007fd909ef9a3b in _XIDHandler (dpy=0x645e60) at ../../src/xcb_io.c:275
#9  0x00007fd90a1bbf77 in XRenderCreatePicture (dpy=0x645e60, drawable=18877711, format=0x7b9080, valuemask=0, attributes=0x0) at ../../src/Picture.c:99
#10 0x00007fd90b448025 in _cairo_xlib_surface_ensure_dst_picture (surface=0x2dafcc0) at cairo-xlib-surface.c:845
#11 0x00007fd90b449874 in _cairo_xlib_surface_fill_rectangles (abstract_surface=0x2dafcc0, op=CAIRO_OPERATOR_OVER, color=<value optimized out>,
    rects=0x7fff176c76e0, num_rects=1) at cairo-xlib-surface.c:1864
#12 0x00007fd90b420685 in _cairo_surface_fill_rectangles (surface=0x7fd90e8dfa00, op=CAIRO_OPERATOR_OVER, color=0x2db00b8, rects=0x7fff176c76e0,
    num_rects=47909392) at cairo-surface.c:1440
#13 0x00007fd90b420891 in _cairo_surface_fill_region (surface=0x2dafcc0, op=CAIRO_OPERATOR_OVER, color=0x2db00b8, region=0x7fff176c80f0)
    at cairo-surface.c:1391
#14 0x00007fd90b42306f in _clip_and_composite_trapezoids (src=0x2db0050, op=CAIRO_OPERATOR_OVER, dst=0x2dafcc0, traps=0x7fff176c8190, clip=0x2daff40,
    antialias=CAIRO_ANTIALIAS_DEFAULT) at cairo-surface-fallback.c:617
#15 0x00007fd90b423390 in _cairo_surface_fallback_fill (surface=0x2dafcc0, op=CAIRO_OPERATOR_OVER, source=0x2db0050, path=0x2db0400,
    fill_rule=CAIRO_FILL_RULE_WINDING, tolerance=0.10000000000000001, antialias=CAIRO_ANTIALIAS_DEFAULT) at cairo-surface-fallback.c:904
#16 0x00007fd90b41febe in _cairo_surface_fill (surface=0x2dafcc0, op=CAIRO_OPERATOR_OVER, source=<value optimized out>, path=0x2db0400,
    fill_rule=CAIRO_FILL_RULE_WINDING, tolerance=0.10000000000000001, antialias=CAIRO_ANTIALIAS_DEFAULT) at cairo-surface.c:1666
#17 0x00007fd90b40db6c in _cairo_gstate_fill (gstate=0x2dafea0, path=0x2db0400) at cairo-gstate.c:982
#18 0x00007fd90b407420 in *INT_cairo_fill_preserve (cr=0x2db0220) at cairo.c:2188
#19 0x00007fd90b407439 in cairo_fill (cr=0x7fd90e8dfa00) at cairo.c:2164
#20 0x00007fd8f7dfba46 in swfmoz_player_render (player=0x2b69800, cr=0x2db0220, region=<value optimized out>) at swfmoz_player.c:816
#21 0x00007fd8f7df8cfd in plugin_x11_handle_event (mozplay=0x2b69800, event=0x7fff176c8520) at plugin_x11.c:57
#22 0x00007fd8f7df7f83 in plugin_handle_event (instance=0x205ad40, eventp=0x7fff176c8520) at plugin.c:412
#23 0x00007fd90d31bcfc in ns4xPluginInstance::HandleEvent (this=0x205ad10, event=0x7fff176c8520, handled=0x7fff176c851c) at ns4xPluginInstance.cpp:1312
#24 0x00007fd90ceeb8cf in nsPluginInstanceOwner::Renderer::NativeDraw (this=0x7fff176c8a00, dpy=0x645e60, drawable=18877711, visual=0x7fd90e8dfa60,
    offsetX=<value optimized out>, offsetY=<value optimized out>, clipRects=0x7fff176c86b0, numClipRects=0) at nsObjectFrame.cpp:4155
#25 0x00007fd90d4ff9ea in NativeRendering (closure=0x7fff176c89a0, dpy=0x0, drawable=47908352, visual=0x7fd90e8dfa60, offset_x=<value optimized out>,
    offset_y=<value optimized out>, rectangles=0x7fff176c86b0, num_rects=0) at gfxXlibNativeRenderer.cpp:59
#26 0x00007fd90d4f2ae7 in _draw_with_xlib_direct (cr=<value optimized out>, default_display=0x645e60, callback=0x7fd90d4ff9c0 <NativeRendering>,
    closure=0x7fff176c89a0, bounds_width=<value optimized out>, bounds_height=40, capabilities=<value optimized out>) at cairo-xlib-utils.c:312
#27 0x00007fd90d4f2d55 in cairo_draw_with_xlib (cr=0x2930890, callback=0x7fd90d4ff9c0 <NativeRendering>, closure=0x7fff176c89a0, dpy=0x645e60, width=170,
    height=40, is_opaque=CAIRO_XLIB_DRAWING_OPAQUE, capabilities=27, result=0x0) at cairo-xlib-utils.c:537
#28 0x00007fd90d4ffad0 in gfxXlibNativeRenderer::Draw (this=0x7fd90e8dfa58, dpy=0x645e60, ctx=0x2b94ff0, width=170, height=40, flags=0, output=0x0)
    at gfxXlibNativeRenderer.cpp:101
#29 0x00007fd90ceed34e in nsPluginInstanceOwner::Paint (this=0x295ae40, aRenderingContext=@0x2ba6f40, aDirtyRect=@0x7fff176c8ad0) at nsObjectFrame.cpp:4076
#30 0x00007fd90ceed39a in nsObjectFrame::PaintPlugin (this=0x26b3d28, aRenderingContext=@0x2ba6f40, aDirtyRect=@0x7fff176c8ad0) at nsObjectFrame.cpp:1400
#31 0x00007fd90ceed423 in PaintPlugin (aFrame=0x26b3d28, aCtx=0x2ba6f40, aDirtyRect=@0x7fff176c8be0, aPt={x = 392989488, y = 32767}) at nsObjectFrame.cpp:1096
#32 0x00007fd90cedcf28 in nsDisplayGeneric::Paint (this=0x2bb8148, aBuilder=<value optimized out>, aCtx=0x2ba6f40, aDirtyRect=@0x7fff176c8be0)
    at ./../base/nsDisplayList.h:862
#33 0x00007fd90ce969f0 in nsDisplayList::Paint (this=<value optimized out>, aBuilder=0x7fff176c8e50, aCtx=0x2ba6f40, aDirtyRect=@0x7fff176c8be0)
    at nsDisplayList.cpp:296

Is this a duplicate of bug 16717 maybe?
As in: Does the patch in that bug fix this crasher?

(In reply to comment #3)
> Is this a duplicate of bug 16717 maybe?
> As in: Does the patch in that bug fix this crasher?

Good catch, it does fix the crash here. Sergio Rafael, Pekka can you confirm too?

The patch works for Pekka too, closing as dup.

*** This bug has been marked as a duplicate of bug 16717 ***