crash, leaving PID file

i'm running a freeradius 1.0.2 as a proxy, with a very simple configuration - no ldap, no sql, only a users file, and some attribnute filters for pre- and post- proxying. strangely i'm finding that about once a day at random times the server is not running, but the PID is left - thus confusing any restart mechanisms. the main log file does not indicate any error. anyone suggest a good why to uncover the problem, short of running it in -X mode and waiting for it to fail. tariq