I've been having this for a while, and it usually worked by either changing around the compatibility mode, multiple tries or a combination of both. This no longer works, the game still gives me the "parameter is incorrect" error and won't launch after numerous tries.
HI! I am assuming you are using windows because i know nothing about mac. So right click the MapleSaga.exe and go to properties, then check "compatibility mode" box and set it to windows 98. (i also check the "run as admin" box). After that click apply and okay and the game should run fine.
Hey. Yeah, I'm running on Windows 8.1, and alternating compatibility modes was one of the first things I tried. Though I've just had a system crash and now the game finally budged and launched(?). Maybe all it needed was a reset. I appreciate the reply.