Introduced in Macrium Reflect v7.1 a timeout is now applied to VSS. This prevents backup jobs from hanging indefinitely and causing scheduled tasks to queue forever if VSS has an internal problem that causes the VSS snapshot creation to stall.
The default time out is 15 minutes, however, on some systems that are experiencing heavy disk I/O during snapshot creation this may not be long enough and you may experience the following error in the log:
First try simply rebooting Windows to clear the problem. If that doesn't help then increase the VSS timeout value.
To increase the timeout value create the following registry entry:
Timeout in seconds, e.g,