M4400 Display Port to HDMI

Hello,
I tried to connect my Precision M4400 to my LG Plasma TV for the last days.
I use a display port male to hdmi female adapter with an hdmi cable.

The weird thing is it works with another hdmi cable on another tv,
but on my tv I cant identify the TV on my laptop.
The same cable and adapter that worked on antoher soniq tv dont work on my tv. Hdmi works fine in general though.

I really need help here. Would a cable HDMI to Display port help?
If yes I dont understand the differnce and I dont see why it worksm on another Soniq TV...

Thanks for your help guys.

 

I've bought dell TK041 adapter.
no problems so far.