The most likely reason is the file server is being rebooted. The trigger tries for 10 seconds to reconnect, and then disables. Is there a way to extend the time that it checks?
Here is the log from c:\program files\Visual Cron\log\
19/09/2012 2:19:03 PM Err Could not UpdateFileTrigger in Trigger: 'New CSV files created in H:\IT\Archive\Axioma\SMA\', ex: The directory name H:\IT\Archive\Axioma\SMA\ is invalid.
19/09/2012 2:19:03 PM Err Error watching directory, err: The directory name H:\IT\Archive\Axioma\SMA\ is invalid.
19/09/2012 2:19:03 PM Err Error watching (ReConnect) directory, err: The path is not of a legal form.
19/09/2012 2:19:07 PM Err Error watching (ReConnect) directory, err: The path is not of a legal form.
19/09/2012 2:19:08 PM Err Error watching (ReConnect) directory, err: The path is not of a legal form.
19/09/2012 2:19:12 PM Err Error watching (ReConnect) directory, err: The path is not of a legal form.
19/09/2012 2:19:13 PM Err Trigger error: The directory name H:\IT\Archive\Axioma\SMA\ is invalid.
19/09/2012 2:19:13 PM Debug Trigger was expired and inactivated