Are you backing up the log or backing up the database? There is a difference.
If you need the ability to restore the database to a point in time you should schedule transaction log backups to occure through out the day.
If you do not need the ability to restore the database to a point in time you should change the recovery mode from full to simple. This will stop SQL Server from keeping the transactions in the log for more than a minute or two. You will not be able to backup the transaction log, therefor you can not restore to a point in time, however you shouldn’t get this error any more. If you do very large operations you may still run into this problem.
If you have set a max growth size for the log file you should remove this setting as well. Also make sure that the disk is not full.
What command did you use to disable the transaction log? There is no command which disables the transaction log.