I have a slightly different callstack (though I've also seen the callstack mentioned above)

kvdveer@kvdveer-desktop:~$ gdb shotwell
GNU gdb (GDB) 7.2-ubuntu
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/shotwell...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/shotwell 
[Thread debugging using libthread_db enabled]
[New Thread 0xb6eefb70 (LWP 4914)]
[New Thread 0xb66eeb70 (LWP 4915)]
[New Thread 0xb5eedb70 (LWP 4916)]
[New Thread 0xb56ecb70 (LWP 4917)]
[New Thread 0xb4eebb70 (LWP 4918)]
[New Thread 0xad6fdb70 (LWP 4936)]
[New Thread 0xaccffb70 (LWP 4937)]
[New Thread 0xac4feb70 (LWP 4938)]
[New Thread 0xabcfdb70 (LWP 4939)]
[New Thread 0xab4fcb70 (LWP 4940)]
[New Thread 0xaacfbb70 (LWP 4941)]
[New Thread 0xaa4fab70 (LWP 4942)]
[Thread 0xac4feb70 (LWP 4938) exited]
[Thread 0xabcfdb70 (LWP 4939) exited]
[Thread 0xad6fdb70 (LWP 4936) exited]
[Thread 0xab4fcb70 (LWP 4940) exited]
[Thread 0xaacfbb70 (LWP 4941) exited]
[Thread 0xaccffb70 (LWP 4937) exited]

Program received signal SIGSEGV, Segmentation fault.
0x00000029 in ?? ()
(gdb) trace
Tracepoint 1 at 0x29
(gdb) d
Delete all breakpoints? (y or n) y
(gdb) frame 
#0  0x00000029 in ?? ()
(gdb) threads
Undefined command: "threads".  Try "help".
(gdb) th
thbreak  thread   
(gdb) th
thbreak  thread   
(gdb) thread 
[Current thread is 1 (Thread 0xb718e860 (LWP 4909))]
(gdb) info threads
  13 Thread 0xaa4fab70 (LWP 4942)  0x0012e416 in __kernel_vsyscall ()
  6 Thread 0xb4eebb70 (LWP 4918)  0x0012e416 in __kernel_vsyscall ()
  5 Thread 0xb56ecb70 (LWP 4917)  0x0012e416 in __kernel_vsyscall ()
  4 Thread 0xb5eedb70 (LWP 4916)  0x0012e416 in __kernel_vsyscall ()
  3 Thread 0xb66eeb70 (LWP 4915)  0x0012e416 in __kernel_vsyscall ()
  2 Thread 0xb6eefb70 (LWP 4914)  0x0012e416 in __kernel_vsyscall ()
* 1 Thread 0xb718e860 (LWP 4909)  0x00000029 in ?? ()
----<SNIP irrelevant stuff>----
(gdb) backtrace 
#0  0x00000029 in ?? ()
#1  0x0020e48c in gexiv2_metadata_get_exif_tag_rational ()
   from /usr/lib/libgexiv2.so.0
#2  0x081fa368 in photo_metadata_get_rational ()
#3  0x081fb387 in photo_metadata_get_exposure_string ()
#4  0x08194af8 in ?? ()
#5  0x0819541a in ?? ()
#6  0x0819454f in ?? ()
#7  0x0819651d in ?? ()
#8  0x081956b8 in properties_update_properties ()
#9  0x0818a7b9 in ?? ()
#10 0x0811da48 in ?? ()
#11 0x01e032d1 in ?? () from /lib/libglib-2.0.so.0
#12 0x01e074e8 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#13 0x01e07cb0 in ?? () from /lib/libglib-2.0.so.0
#14 0x01e08373 in g_main_loop_run () from /lib/libglib-2.0.so.0
#15 0x016a8e89 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#16 0x0808f52b in library_exec ()
#17 0x0808fc37 in _vala_main ()
#18 0x0808fcdc in main ()


This happens with _every_ picture in my collection. Example exif data:
kvdveer@kvdveer-desktop:~/Pictures/2010/09/18$ exiv2 IMG_3748.JPG 
File name       : IMG_3748.JPG
File size       : 3041642 Bytes
MIME type       : image/jpeg
Image size      : 3072 x 2048
Camera make     : Canon
Camera model    : Canon EOS DIGITAL REBEL
Image timestamp : 2010:09:18 09:17:26
Image number    : 137-3748
Exposure time   : 1/60 s
Aperture        : F4.5
Exposure bias   : 0 EV
Flash           : No flash
Flash bias      : 0 EV
Focal length    : 28.0 mm
Subject distance: 0
ISO speed       : 800
Exposure mode   : Program (P)
Metering mode   : Multi-segment
Macro mode      : (0)
Image quality   : Fine
Exif Resolution : 3072 x 2048
White balance   : Auto
Thumbnail       : image/jpeg, 7168 Bytes
Copyright       : 
Exif comment    :