[mythtv] Backend crashing except when under gdb

[freedenizen]

So, I've been having a problem with my backend crashing a lot.  I'm
trying to get a real backtrace under gdb now, but haven't been able to
get it to get it to crash.  In the logs when it crashes (not under gdb
of course) I see:
*** glibc detected *** /usr/local/bin/mythbackend: corrupted
double-linked list: 0x085c84b8 ***
======= Backtrace: =========
/lib/libc.so.6(+0x6c534)[0xb4bc8534]
/lib/libc.so.6(+0x6ca79)[0xb4bc8a79]
/lib/libc.so.6(+0x6eab6)[0xb4bcaab6]
/lib/libc.so.6(__libc_malloc+0x5e)[0xb4bcce5e]
/usr/lib/qt4/libQtCore.so.4(_Z7qMallocj+0x1e)[0xb4f28634]
/usr/lib/qt4/libQtCore.so.4(_ZN7QString17fromLatin1_helperEPKci+0x3f)[0xb4f73689]
/usr/lib/qt4/libQtCore.so.4(_ZN7QString16fromAscii_helperEPKci+0xd9)[0xb4f7a33b]
/usr/local/lib/libmythupnp-0.24.so.0(_ZN4SSDP11ProcessDataEP13MSocketDevice+0xf1)[0xb69e1cc1]
[0xb2a05f88]
/usr/local/bin/mythbackend(_ZN7QThread11qt_metacastEPKc+0x0)[0x8057674]

Anyone have any idea where to look?  I've tried recompiling various
dependencies and then recompiling myth, deleted everything myth
related from /usr/local/lib/, but no luck.  I have a feeling this
could entirely be a fault on my system but I'm not sure where to begin
poking.