Ok, you've mentioned 2 issues in your original post, I'll answer them separately.
1: OnDemand issues. The TiVo has an inbuilt internet connection, and many problems with VOD dropping are caused by this connection failing with your realising. Do you have any flashing lights on the front-left of your box?
2: Pixellation on live TV - this often indicates a signal issue, and if you've reboot your box and the issues have persisted, this alone is a service fault which either merits an engineer visit or replacement TiVo.
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