I'm not sure, but I suspect this is a bug in php.
Does php leave a coredump? Try analyzing that (gdb -c), try recompiling PHP & extensions with debugging symbols (-DWITH_DEBUG).
Also, what exactly are you doing in drupal to cause this error?
Also, these options might be useful in php.ini
Code:
report_zend_debug = 1
fastcgi.logging = 1