Commish of TX wrote:
Mr. Pondini,
In a closed, archived Apple Support discussion I saw your advice to run Time Machine (TM) excluding Applications. I did it and it appears to have solved my problem. So I just wanted to say thank you. I am not sure why it worked but so far so good.
I don't recommend that as a normal practice -- I suspect it was meant to help diagnose a problem -- most likely, a problem with a file in an Application.
I discovered it was the hourly TM backups causing it; or I could trigger a shut down by simply instructing TM to Back Up Now and then waiting for it to hit a particular spot in the process
It's extremely rare for a problem with Time Machine to cause a system crash -- it almost always fails with a message, or on rare occasions the backup process will crash.
Is your entire system crashing, so you have to restart, or is your user getting logged-off?
Obviously, you need to find what that "particular spot" is. With a bit of luck, there may be a message in your logs. Use the widget in #A1 of Time Machine - Troubleshooting to display the backup messages from your logs. Locate the most recent failed backup in question, then copy and post all the messages here.
Also, what version of OSX are you running, and what are you backing-up to (external HD, Time Capsule, etc)?
If nothing there has a file name in it, you might want to use the Console application per the pink box in #A1 to look at the logs directly. But don't filter for backupd as mentioned there; locate the backup messages, then see if there are other messages about the same time, sent by other processes. If so, copy and post that portion here (not a screenshot, and not pages and pages, please).
However, It's quite possible that the message doesn't make it to the log before the crash -- if not, you may have to do some trial and error to find the problem. That may be easier if you have another drive (or partition) you can use temporarily. It won't need to be very large.