When we play back a program recorded earlier this week, the playback is (usually) very unsatisfactory. Sound especially is stuttering and sometimes the picture also.
Watching programs on catch up sometimes has the same problem.
Is anyone else having problems, or is there a problem with my TiVo box?
You've posted in the TV360 section, but referred to a TiVo - which do you have?
Problems with recordings usually mean either a signal fault affecting your live TV picture which is then recorded, or a hard drive issue that will affect all recorded content.
Neither of those would affect OnDemand, so you may have another issue. Further advice would partly depend which box you have.