gthumb crashes with segfault at startup, without any information on the error.
Using gdb I got the following message:

$ gdb gthumb
GNU gdb (GDB) 7.1-debian
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 "i486-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /usr/bin/gthumb...Reading symbols from
/usr/lib/debug/usr/bin/gthumb...done.
done.
(gdb) run
Starting program: /usr/bin/gthumb
[Thread debugging using libthread_db enabled]
[New Thread 0xb3266b70 (LWP 7373)]
[New Thread 0xb31e5b70 (LWP 7378)]
[New Thread 0xb3164b70 (LWP 7379)]
[New Thread 0xb30e3b70 (LWP 7380)]
[New Thread 0xb3062b70 (LWP 7381)]

Program received signal SIGSEGV, Segmentation fault.
0x080c7918 in gth_pref_get_real_toolbar_style () at gth-preferences.c:142
142     gth-preferences.c: No such file or directory
        in gth-preferences.c
(gdb) bt
#0  0x080c7918 in gth_pref_get_real_toolbar_style () at gth-preferences.c:142
#1  0x0808cfca in _gth_browser_update_toolbar_style (browser=0x8189000) at gth-
browser.c:3278
#2  0x0808f66e in _gth_browser_construct (browser=0x8189000) at gth-
browser.c:4065
#3  0x0808fa6d in gth_browser_new (uri=0x0) at gth-browser.c:4145
#4  0x080dafb8 in open_browser_window (location=0x817d4c0) at main.c:257
#5  0x080db203 in prepare_application () at main.c:340
#6  0x080db4d0 in main (argc=1, argv=0xbffff494) at main.c:433

Running gthumb as a different user avoids the segfault, so there must be a
problem with the user's personal data. I tried purging the package, but it
still crashes.