This probelm has recently started for me as well..
Da2 was running fine until i tried to play the DLC 'Mark of the Assassin' then it would freeze.. i tried to fix that by downloading the newest version of DA2 from the official site previously mentioned in this forum (will link at later time when i get back to it) and after that my DA2 wouldnt start.. no error message or anything
edit: i looked at my game in the program files and say the launcher outside of any file within the dragon age 2 file when i clicked on it it said couldnt find launcher.. did some looking and found out the update updated my game but my launcher wasnt so it wouldnt start.. simply uninstall and re-downloading from origin fixed this for me.. hope this helps