Question : SQL logs backups have suddenly begun failing.

I am running SQL 2005 on windows 2003 server and have been running backups with backup exec ver. 11d the log file backups have just started failing with the following error

Backup Exec Alert: Job Failed
(Server: "SAPQA01") (Job: "PRD Log Backup hourly") PRD Log Backup hourly -- The job failed with the following error: A log backup was attempted on a database that is not currently configured to support log backups. To change the configuration use Enterprise Manager to set the recovery mode to FULL in SQL 2000 or turn off the 'trunc on chkpt' option in SQL 7.  A new full backup should be performed if these settings are changed before a log backup is run.
 
I have tried restarting the Backup exec services already to correct the problem

Answer : SQL logs backups have suddenly begun failing.

the error message tells you what to do:

change the recovery mode from the database from simple to full.