I'd say it's either the HDMI cable or the Lenovo software used to send the video.
Maybe you can explain a bit more detail about what's going on. In the mean time maybe try a program like VLC (videolan) if that makes sense for what you're doing.
*also, if you can setup the monitor as a 2nd screen then the video isn't streaming to be decoded by the HDTV but rather just played on the Lenovo and the screen is simply output.
So if you can setup the monitor as a 2nd screen and the video can play on the Lenovo by itself already you should have no issues. Just add as a 2nd screen (or the ONLY screen), launch VLC or whatever and select Fullscreen and it should work fine.