"When it turns itself off" indicates your timer is firing and recording, then it shuts itself off automatically, as designed, unless you're there to tell it not to.
Since you say this is 2nd unit to do this, and that's improbable, I suspect you're setting individual, one-time timers that then go away and it looks as if there are no timers anymore?
Set a short (even 1-min.) M-F timer for anything today and see if that timer sticks around for a Friday repeat. You arrow down repeatedly in the Date box to see all recurring timer options.
Only other way to lose recurring timers is if you have the Mag on a power strip and you're shutting unit OFF with the switch on the power strip? Clock and timers get lost if no power for 1-2 hours.
There's also a weird situation where, if your clock gets auto-set to wrong date and time, ALL timers could disappear when the OS sees that those times are PAST. Do you have Auto Clock ON and set for a PBS channel by chance (PBS is virtually always wrong these days, year 2037 here)?
Edited by wajo - 11/22/12 at 9:22am