[exim] Failed to read delivery status

I keep having issues with certain domains for only an hour or so at a time.
I see several messages in my panic_log that say this.

2008-09-21 07:21:33 1KhN0J-0005fh-1X failed to read delivery status for
user@??? from delivery subprocess
2008-09-21 07:21:33 1KhN0J-0005fh-1X appendfile transport process returned
non-zero status 0x000e: terminated by signal 14


Exim then freezes the message and sends a bounce for that user. After the
message thaws 7days alter, it sends without issue. I thought perhaps it was
something with the db so i set a cron to tidy the db every hour. it doesn't
seem to be helping. Any thoughts on how to debug this issue?

ChrisZ