Nothing, to my knowledge; It usually just works. Although, this was discovered while investigating an issue where the server ran out of disk space. I suspect it is due to a badly configured QF session, and I was trying to shut it off for a while.

If you stop the QF Agent service, free up some disk space, and then start the service again, are you able to view the schedules? 

Nope. It still shows the same error.

Can you take a look at the files in "C:\ProgramData\Laserfiche\Quick Fields Agent\Schedules"? There should be an XML file for each schedule.