I'm getting a failed assertion:

keyboard.c:5548: Emacs fatal error: assertion failed: c == event->code

Breakpoint 1, w32_abort () at w32fns.c:9127
9127      button = MessageBox (NULL,
(gdb) bt
#0  w32_abort () at w32fns.c:9127
#1  0x0101f2fb in die (msg=0x13598f8 "assertion failed: c == event->code",
    file=0x135686a "keyboard.c", line=5548) at alloc.c:6287
#2  0x01091bfc in read_char (commandflag=1, nmaps=2, maps=0x82fb70,
    prev_event=25171969, used_mouse_menu=0x82fc18, end_time=0x0)
    at keyboard.c:5548
#3  0x010928d1 in read_key_sequence (keybuf=0x82fce4, bufsize=30,
    prompt=25171969, dont_downcase_last=0, can_return_switch_frame=1,
    fix_current_buffer=1) at keyboard.c:9459
#4  0x010952e1 in command_loop_1 () at keyboard.c:1666
#5  0x0101b0b7 in internal_condition_case (bfun=0x1095082 <command_loop_1>,
    handlers=25244841, hfun=0x108cba3 <cmd_error>) at eval.c:1493
#6  0x0108bdd0 in command_loop_2 () at keyboard.c:1381
#7  0x0101b152 in internal_catch (tag=25236817,
    func=0x108bdad <command_loop_2>, arg=25171969) at eval.c:1229
#8  0x0108c9dc in command_loop () at keyboard.c:1360
#9  0x0108cd06 in recursive_edit_1 () at keyboard.c:969
#10 0x0108ce71 in Frecursive_edit () at keyboard.c:1031
#11 0x01002b0c in main (argc=8585136, argv=0xa92778) at emacs.c:1781

That's on Windows XP, with an up-to-date trunk build, built with "gcc
(GCC) 4.2.1-sjlj (mingw32-2)".

The error happens (repeatably) whenever I press Ctrl + a non-ASCII key
(for example, C-Ñ, C-ç, C-º).

             Juanma