Have been seeing segmentation faults coming from "drush cron" runs recently.
Seems that the issue is related to a conflict between the curl and pgsql php components.
On debian - the php cli config loads the config files under /etc/php5/cli/conf.d
If it loads curl.so before it loads pgsql.so then when releasing a postgres connection it will segfault.
Workaround is simply to load pgsql first. Files in the conf.d directory are loaded alphabetically.