What client version are you using?  There was a bug in dsmcutil at the 4.2.0
base level, as I recall.

Try updating the pw this way:

open a DOS window
CD to TSM baclient directory
type:  dsmc sched

That should start the scheduler, and prompt for the password. You will
connect and get a scheduled start time.  Then just kill the window.

Then repeat the same thing; the second time, it should NOT prompt for the
password, if it got saved correctly the first time.