Service reboot leaves postmaster.pid

Hello,
    I'm running the postmaster as a service using cygrunsrv and this
seems to go fine apart from when I reboot it doesn't seem to remove the
postmaster.pid file, meaning it fails to start automatically after reboot.
Stoping and starting the service manually work fine. Anyone else had this
problem or any pointers where to look (don't know much about NT services).
Thanks,
- Stuart