Sorry you are experiencing this.
It appears you are running into a known issue with 7.3 and the activity history which has been reported by several users.
Some users have seen slightly increased performance by Reducing the amount of data in the activity cache.
http://www.red-gate.com/supportcenter/content/SQL_Backup/help/7.2/SBU_ActivityCacheLocation
This issue is currently under investigation and we plan to release a fix once one becomes available.
If you wish to downgrade to a previous version you can find the installer here.
ftp://support.red-gate.com/patches/SQLBackup/04Sep2012/SQLBackup_7.2.0.286.zip
It appears you are running into a known issue with 7.3 and the activity history which has been reported by several users.
Some users have seen slightly increased performance by Reducing the amount of data in the activity cache.
http://www.red-gate.com/supportcenter/content/SQL_Backup/help/7.2/SBU_ActivityCacheLocation
This issue is currently under investigation and we plan to release a fix once one becomes available.
If you wish to downgrade to a previous version you can find the installer here.
ftp://support.red-gate.com/patches/SQLBackup/04Sep2012/SQLBackup_7.2.0.286.zip