No se puede crear NSUrl desde NSString que siempre se vuelve nula
NSMutableString *string = [[NSMutableString alloc]initWithString:
@"http%3A%2F%2Fsupport24hour.com%2Fworkplace2%2Fbuttler%2Fimage.php%3Fwidth%3D534%26height%3D256%26image%3Duploads%2Fdeals%2FdealImage%2Fdeal_1383005121_IGA+Logo.JPG"];
[string replaceOccurrencesOfString:@"+" withString:@" " options:NSCaseInsensitiveSearch range:NSMakeRange(0, [string length])];
NSURL * url = [NSURL URLWithString:[string stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];