Recently my TiVo HD with an upgraded 1 GB drive seems to have glitches in programming. Sometimes the show just stops. Picture will be blank for 30 seconds or so. Other times there is pixelation. It is still intermittent, but it seems to have gotten worse over the last 3 months. I thought I remember reading in these forums that there were some test codes or diagnostics that you can enter into your TiVo and it would run some tests. I have searched, but have not been able to locate them. If my memory is correct would someone please point me to them. TIA!