I use Symantec System restore to backup our servers, but on an app specific server like Exchange I also do a daily backup using Windows backup (this way the logs get truncated properly). I've seen a problem the last few weeks where the window backup is failing. It does it every few days. The error says operations stopped, and on the system state access denied. My first gut feeling was that symantec somehow had a vss lock, but after checking the logs the symantec backup finished a good 5 hours before the windows one kicked off.
So i tried to open the etl files but I've never really dealt with them before, and I don't really see any errors. Attached are the logs. I had to rename the .etl to .txt to get the upload to work so you will need to change it back.