To ensure that you have excluded it properly, start the TSM Gui and go to
the backup window.  Drill down to the TSM directory - the dsmsched.log file
should have an red X in it.  If it doesn't you probably have the wrong
syntax for the exclude.

If the X, is there, is this a scheduled backup and if so have you restarted
the TSM Schedule service so that it reads the updated option file?