Alright I have solved the issue. My MDP-->HDMI adapter works fine now with my LG.
Here is what I did:
In my LG input menu, for HDMI, there's a little arrow indicating PC or DTV. Mine was always set at PC, while everything connected I changed it to DTV and unplugged my screen, waited for awhile then I plugged it back and Voilà!
I hope this helps.