Running unstable's -9.0- kernel makes midori (and in the same way iceweasel) creash on startup with "Unknown signal" in pthread_create. This is a pretty default wheezy system (with minor sid parts).
Please try to run it without gdb and analyze core after segfault.
I guess that it would be in a different place.
It is a limitation of our gdb port, it does not know,
that this signal is internal to threading library.
The problem of iceweasel might be due to:
* config/config.mk, config/rules.mk, js/src/config/config.mk,
js/src/config/rules.mk: (Statically) link jemalloc to all programs.
The jemalloc uses internally pthread library
and pthread library uses internally malloc.
Petr