I had to copy this from the terminal.  Info about threads 1, 2 and 3 wasn't being written to pan_backtrace.

jd@gertrude:~/misc$ script pan_backtrace
Script started, file is pan_backtrace
jd@gertrude:~/misc$ uname -a
Linux gertrude 2.6.15-28-686 #1 SMP PREEMPT Thu Feb 1 16:14:07 UTC 2007 i686 GNU/Linux
jd@gertrude:~/misc$ gdb pan
GNU gdb 6.4-debian
Copyright 2005 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...(no debugging symbols found)
Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".

(gdb) handle SIGUSR1 nostop noprint
Signal        Stop      Print   Pass to program Description
SIGUSR1       No        No      Yes             User defined signal 1
(gdb) handle SIG32 nostop noprint
Signal        Stop      Print   Pass to program Description
SIG32         No        No      Yes             Real-time event 32
(gdb) run
Starting program: /usr/bin/pan
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---Type <return> to continue, or q <return> to quit---
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[Thread debugging using libthread_db enabled]
[New Thread -1219737920 (LWP 10412)]
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[New Thread -1223898192 (LWP 10416)]
[New Thread -1232290896 (LWP 10417)]
[New Thread -1240683600 (LWP 10419)]
[New Thread -1249076304 (LWP 10420)]
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** (pan:10412): CRITICAL **: static void PanTreeStore::sortable_set_sort_column_id(GtkTreeSortable*, gint, GtkSortType): assertion `tree->sort_info->count(sort_column_id) != 0' failed
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Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1219737920 (LWP 10412)]
---Type <return> to continue, or q <return> to quit---
0x00000000 in ?? ()
(gdb) thread apply all bt

Thread 5 (Thread -1249076304 (LWP 10420)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb76f5c76 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb78b5d4f in g_async_queue_push_sorted () from /usr/lib/libglib-2.0.so.0
#3  0xb78e9410 in g_thread_pool_free () from /usr/lib/libglib-2.0.so.0
#4  0xb78e75a2 in g_static_private_free () from /usr/lib/libglib-2.0.so.0
#5  0xb76f3341 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#6  0xb76884ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 4 (Thread -1240683600 (LWP 10419)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb76f5c76 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb78b5d4f in g_async_queue_push_sorted () from /usr/lib/libglib-2.0.so.0
#3  0xb78e9410 in g_thread_pool_free () from /usr/lib/libglib-2.0.so.0
#4  0xb78e75a2 in g_static_private_free () from /usr/lib/libglib-2.0.so.0
#5  0xb76f3341 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#6  0xb76884ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 3 (Thread -1232290896 (LWP 10417)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb76f5c76 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb78b5d4f in g_async_queue_push_sorted () from /usr/lib/libglib-2.0.so.0
#3  0xb78e9410 in g_thread_pool_free () from /usr/lib/libglib-2.0.so.0
#4  0xb78e75a2 in g_static_private_free () from /usr/lib/libglib-2.0.so.0
#5  0xb76f3341 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
---Type <return> to continue, or q <return> to quit---
#6  0xb76884ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 2 (Thread -1223898192 (LWP 10416)):
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb76f5c76 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb78b5d4f in g_async_queue_push_sorted () from /usr/lib/libglib-2.0.so.0
#3  0xb78e9410 in g_thread_pool_free () from /usr/lib/libglib-2.0.so.0
#4  0xb78e75a2 in g_static_private_free () from /usr/lib/libglib-2.0.so.0
#5  0xb76f3341 in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#6  0xb76884ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread -1219737920 (LWP 10412)):
#0  0x00000000 in ?? ()
#1  0x080e1e1b in std::__introsort_loop<__gnu_cxx::__normal_iterator<PanTreeStore::Row**, std::vector<PanTreeStore::Row*, std::allocator<PanTreeStore::Row*> > >, int, PanTreeStore::RowCompareByColumn> ()
#2  0x080dee28 in PanTreeStore::insert_sorted ()
#3  0x080df555 in PanTreeStore::insert_sorted ()
#4  0x080d0c62 in pan::HeaderPane::on_tree_change ()
#5  0x0814e961 in pan::DataImpl::MyTree::add_articles ()
#6  0x0814f4c3 in pan::DataImpl::MyTree::apply_filter ()
#7  0x0814fa0d in pan::DataImpl::MyTree::add_articles ()
#8  0x081313af in pan::DataImpl::on_articles_added ()
#9  0x0815c6a4 in pan::DataImpl::xover_add ()
#10 0x0816f3f8 in pan::TaskXOver::on_nntp_line ()
#11 0x0817175a in pan::NNTP::on_socket_response ()
---Type <return> to continue, or q <return> to quit---
#12 0x08196b0f in pan::GIOChannelSocket::do_read ()
#13 0x081974c5 in pan::GIOChannelSocket::gio_func ()
#14 0xb78f252c in g_vasprintf () from /usr/lib/libglib-2.0.so.0
#15 0xb78cb8d6 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#16 0xb78ce996 in g_main_context_check () from /usr/lib/libglib-2.0.so.0
#17 0xb78cecb8 in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#18 0xb7d0c765 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#19 0x080b3b19 in (anonymous namespace)::run_pan_in_window ()
#20 0x080b4735 in main ()
(gdb)

