The issue may be related to a recent Event Source Update you installed.

To check if there were any issues doing your last Event Source Update, look in the logs directory (normally E:\%_envision%\logs) for a file by the name of autoupdatelog.log

Entries in this file marked by ERROR are the ones to which you want to pay particular attention.

One of the most common problems with having an Event Source update fail is having a device directory or file flagged as read-only. If the updater tries to update the files, it will error out because the file is currently marked as read-only.

All files and folders in the \etc\devices folder should be fully writable.