I can replicate a mythbackend segfault every time I use mythweb to go into "backend status". Even with all logging switched on nothing useful appears in mythbackend.log.

The most (not terribly) useful thing I've managed to get is from running strace against mythbackend when it fails:

gettimeofday({1196589504, 470225}, NULL) = 0
gettimeofday({1196589504, 470368}, NULL) = 0
select(14, [6 7 13], [], [], {20, 389404}) = 1 (in [6], left {20, 343333})
accept(6, {sa_family=AF_INET, sin_port=htons(47069), sin_addr=inet_addr("192.168.160.1")}, [16]) = 16
fcntl64(16, F_SETFD, FD_CLOEXEC) = 0
futex(0x81a7b9c, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, 0x818ad14, 0) = 1
futex(0x818ad14, FUTEX_WAKE_PRIVATE, 1) = 1
gettimeofday({1196589504, 519775}, NULL) = 0
gettimeofday({1196589504, 519952}, NULL) = 0
select(14, [6 7 13], [], [], {20, 339820}) = ? ERESTARTNOHAND (To be restarted)
+++ killed by SIGSEGV +++

backtrace:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb2f8fb90 (LWP 7000)]
0xb5d9936d in fclose@@GLIBC_2.1 () from /lib/libc.so.6
(gdb) bt
#0 0xb5d9936d in fclose@@GLIBC_2.1 () from /lib/libc.so.6
#1 0x0807cca3 in ?? ()
#2 0x080844fc in ?? ()
#3 0x080845f0 in ?? ()
#4 0xb6ef2355 in HttpServer::DelegateRequest () from /usr/lib/libmythupnp-0.20.2.so.0
#5 0xb6ef3345 in HttpWorkerThread::ProcessWork () from /usr/lib/libmythupnp-0.20.2.so.0
#6 0xb6eef4ec in WorkerThread::run () from /usr/lib/libmythupnp-0.20.2.so.0
#7 0xb63bfd85 in QThreadInstance::start () from /opt/qt/lib/libqt-mt.so.3
#8 0xb5f9b162 in start_thread () from /lib/libpthread.so.0
#9 0xb5e0626e in clone () from /lib/libc.so.6
(gdb)

Core dump: http://charrett.com/core.mythbackend.bz2 (2.4MB)