The forums suggested changing the DragonAge ini settings to 1400 by 900, and fullscreen to 1. I'm clean installing and trying that. Hope it works. Wish I found this forum topic sooner. It would save me from contacting you. I've been looking for a resolution for weeks.
Here's the forum I found the suggestion at: http://social.bioware.com/forum/1/topic/99/index/12929343/1
I`ve got the same problem. Dragon age Origins ran fine in the previous OSX-version but now won`t run after I downloaded Mavericks. Getting the same error message with "error -50". Will try changing the settings as described though not very hopeful. I`m also running the game on a retina mac which went fine until OS X 10.9 came, so it doesn`t appear to be the same problem as described in your link.
Any luck on your part so far?
Success!
Solved thanks to your forum link. As recommended there, I set FullScreen to 1 and changed ResolutionWidth=1440 and ResolutionHeight=900 in Dragonage.ini and the game launches properly.
