Did you actually programme a code for your TV or did you simply use the default setting of the remote which often turns TVs on/off and controls the volume?
If you didn't put in a code for the TV, that would explain why the video source button reverts to cable functionality. Suggest you reset the remote to default and start over.
1. Programme in the correct code for the TV.
2. Do the master power programming, but read the instructions carefully. Often people forget to press the last "CBL" button, or do an incorrect sequence. Suggest you read the instructions to someone else.
3. Then do the Global volume lock to the TV.
In this way, the Remote will turn both devices on/off and will control the TV volume while leaving the remote in "CBL" mode.
If the TV accepts "video source" commands, of course you'll have to press the TV button to do that.
I assume you don't have an AVR. If you do, you'll want to add that to the Master power sequence and put the volume lock on it rather than the TV.
See the following post, useful for those new to the forum - FAQs, Search Tips, Optimization, etc:
http://www.digitalhome.ca/forum/showthread.php?t=57741