Code:
function loadLevel(STRING* name);
{
STRING* fullpath = name;
str_cat(fullpath, "\\config.cfg"); // At this line I recieve a "Invalid Arguments in loadLevel" error?
}

function main()
{
loadLevel("map1");
}

Erroneous semicolon after function loadLevel.
"map1" might be an immutable char* const(ant), which might not be passed as a STRING* argument to function loadLevel.