This happens to me all the time. The exact same problem. It is getting old to have to double check my timers every week - only to find that a handful are not going to fire. The only solution, like you mentioned, is to delete that bad / corrupt timer and make a new timer. This has been happening me for over 2 years. I went as far as replacing my 722 with a new unti....same thing happens. At one time, the Dish care folks said it was a known firmware problem...and they were working on a FIX.
The ONE thing I want my DVR to do, is fire a timer when I program it to. If the DVR can't do that basic function reliably - there is a problem.
Some people claim this may be a function of bad GUIDE info, but I have my doubts, because if I set a new timer to replace the old one - problem solved.
I am a huge Dish Network fan and subscriber for over 12 years, but this problem keeps me from signing a new 24 month contract with them. There will be one day when I get tired of going through all my timers and missing shows...then it will be time for a change.
There have been a few other threads about this issue, but I am surprised how few people this affect.
Chris...