Looks like someone may have tracked down the problem:

https://bugs.archlinux.org/task/21924#comment69358

I think the problem is caused by line 205 of xbindkeys.c
{
  size_t envstr_size = strlen(DisplayString(xany->display)) + 8 + 1;
  [b]char* envstr = malloc (envstr_size);[/b]
  XWindowAttributes attr;
  char* ptr;
  char buf[16];

Increasing the allocated memory by 2 (char* envstr = malloc (envstr_size+2);) seems to solve the issue.

(gdb) backtrace
#0  0xb7fa6c38 in _duma_strncat () from /usr/lib/libduma.so.0.0.0
#1  0xb7fa6e7a in strncat () from /usr/lib/libduma.so.0.0.0
#2  0x080497db in adjust_display (xany=0xbffff228) at xbindkeys.c:222
#3  0x08049ace in event_loop (d=0xb6ddf6bc) at xbindkeys.c:320
#4  0x08049573 in inner_main (argc=0, argv=0x0) at xbindkeys.c:134
#5  0xb7e09d26 in invoke_main_func () from /usr/lib/libguile.so.17
#6  0xb7ddad12 in c_body () from /usr/lib/libguile.so.17
#7  0xb7e51723 in scm_c_catch () from /usr/lib/libguile.so.17
#8  0xb7ddb312 in scm_i_with_continuation_barrier () from /usr/lib/libguile.so.17
#9  0xb7ddb3f3 in scm_c_with_continuation_barrier () from /usr/lib/libguile.so.17
#10 0xb7e502f9 in scm_i_with_guile_and_parent () from /usr/lib/libguile.so.17
#11 0xb7e503ee in scm_with_guile () from /usr/lib/libguile.so.17
#12 0xb7e09cbf in scm_boot_guile () from /usr/lib/libguile.so.17
#13 0x080495d3 in main (argc=2, argv=0xbffff604) at xbindkeys.c:154