+5  A: 

You need to replace space (and other invalid in url characters) by percent escapes. NSString has -stringByAddingPercentEscapesUsingEncoding: method for that

Vladimir
To add a little more explanation to this correct but short answer, the string @"http://www.abc.net/feed/index_clatest.php?more=s-laday gaga" is not a valid URL because it contains a space. Cocoa validates URLs before trying to use them.
JeremyP