ive tried a few times to load AC, but keeps stopping to load at 'setting defaults'. Loaded through Steam not Content Manager as I haven't loaded it on yet since computer upgrade.
The only time I ( and a friend of mine ) had this problem regularly ( all the time in fact ) with AC ... the reason was the used DXGI.dll
Once out of the game or replaced by a d3d11.dll when it was possible .... this problem disappeared and the game launched as before.
NB: don't ask me why ... but now, although I have this dxgi.dll in game for a long time .... the problem never showed up again !
Worth a try or have a look before searching for something else.