[rdiff-backup-users] Should I kill the rdiff-backup process? Fatal Error: a previous rdiff-backup session is still running

[Dave]

I got an email from my server with this error:

Fatal Error: It appears that a previous rdiff-backup session with process
id 27412 is still running.  If two different rdiff-backup processes write
the same repository simultaneously, data corruption will probably
result.  To proceed with regress anyway, rerun rdiff-backup with the
--force option.

I checked and the process is indeed still running:
$ ps -e | grep rdiff
27412 ?        08:18:02 rdiff-backup

So I looked at the logs for the last backup and I was surprised to see that is apparently finished.
StartTime 1240380901.00 (Wed Apr 22 02:15:01 2009)
EndTime 1240381370.99 (Wed Apr 22 02:22:50 2009)
ElapsedTime 469.99 (7 minutes 49.99 seconds)

Should I kill the process? Can anyone think of an explanation for this? Thanks.