Did you try with HDMI extension? Other HDMI port, setting the right HDMI source to ouput? Also if you use other power cable it might not get enough power to stay on or work normal, always use included power adapter & cable.
1: Power off the tv.
2: Connect the meegopad via HDMI & use the official power cable.
3: Turn on the meegopad, wait a few second.
4: Turn on the tv & set the right HDMI source.
It's important to have the meegopad boot first before the tv does, some tv's have this issue with some devices.