Lynn Pettis (2/20/2013)
Sounds like your database is using BULK_LOGGED or Full Recovery model and you aren't running any transaction log backups. Full backups and Differential backups do not truncate the transaction log. This only occurs when you run a transaction log backup.
If so, then you should take regular transaction log backups, such as every 30 minutes, depending on how important the databse is.