I checked sys.databases to find out which databases need LOG backups. It surprised me that I had quite a few where
log_reuse_wait_desc=LOG_BACKUP meaning, the JOB I have set up to run LOG backups on these databases isn't actually creating LOG backup files.
After doing some searching, it had been suggested to change database modes from FULL to SIMPLE, then back to FULL to reset things. After doing this I am still unable to get a LOG backup to successfully run.
I am using SQL Server 2005, and use the ola hallengren method of backup found here http://ola.hallengren.com/sql-server-backup.html.