Website Backup Hangs on OS X 10.5

I am having a strange problem on OS X 10.5 with the scheduled backups feature in virtualmin. The backup script executes correctly each night for about 2 or three weeks, after which the script will just hang. The following error is logged for luanchd in the OS X log:

could not setup mach task special port 9: (os/kern) no access

The only way to fix is to reboot the system.

Yeah, I see a few posts about an error like that on Apple’s discussion forums all from people having trouble running apps from Cron, but none seem to clarify a cause:

It doesn’t sound like a Virtualmin issue, but just in case, I’d recommend filing a Bug report and see if anything stands out to Jamie.