This game are a bit old, and the developer (BioWare) doesn't really care for it and/or patch it any more. (But they do sell it of course...)

Most modern (new) monitors are wide-screen, and the game has some issues with that. I recommend to look at this guide if you need a different screen resolution, then the built-in ones:
http://steamcommunity.com/sharedfiles/filedetails/?id=427275987

It's also recommended to switch off frame buffer and/or soft shadows. I wasn't able to start a new game without switching those off. :(

Merry Christmas!