If the Symantec Backup Exec job history takes a long to load and when it does, it is blanked. This usually means the database is too large and needs to be compacted. Use the commands at your own risk.
This is for Symantec 11d 7170. At the command prompt, change to Symantec Backup Exec folder.
osql -E -S localhost\bkupexec use BEDB select Count(*) from JobHistorySummary select Count(*) from JobHistoryDetailInfo go truncate table JobHistoryDetailInfo truncate table JobHistorysummary DBCC SHRINKDATABASE (BEDB,5) DBCC CHECKDB go
This can take some time as the old records get purged.