facebook - iOS: Facebook error "missing message or attachment"

Question

Upgrading my app. Target is iOS5.1. Xcode 4.5.2 and am using FacebookSDK 3.0 along with Twitter Frameworks. App is logging into Facebook without issue. When I attempt to publish a post, I get this returned in the log:

2012-12-18 10:39:31.934 MyApp[31754:1d603] Error Domain=com.facebook.sdk Code=5 
"The operation couldn’t be completed. (com.facebook.sdk error 5.)" 
UserInfo=0xab74630 {com.facebook.sdk:ParsedJSONResponseKey={
    body =     {
        error =         {
            code = 100;
            message = "(#100) Missing message or attachment";
            type = OAuthException;
        };
    };
code = 400;
}, com.facebook.sdk:HTTPStatusCode=400}
2012-12-18 10:39:31.935 MyApp[31754:1d603] (null)

This last line is the result of a log expression to list the "postParams" in the "publishStory" method listed below. Note that it is (null). The error result in simulator is "error: domain = com.facebook.sdk, code = 5"

I used the Facebook tutorial to build the FB interface. I've got the params listed in initWithNibName, just as the tutorial indicates.

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // this stuff will change... just get it working

        self.postParams = [[NSMutableDictionary alloc] initWithObjectsAndKeys:
                           @"Share...", @"message",
                           @"http://MyApp.com", @"link",
                           @"icon.png", @"picture",
                           @"MyApp", @"name",
                           @"A wonderful way to record your life events.", "caption",
                           @"Easy to use.", @"description",
                           nil];
    }
    return self;
}

Then, the "publish" is in a separate method, which is where it stops and I get the above error.

- (void)publishStory
{
    [FBRequestConnection
    startWithGraphPath:@"me/feed"
    parameters:_postParams
    HTTPMethod:@"POST"
    completionHandler:^(FBRequestConnection *connection,
                     id result,
                     NSError *error) {
        NSString *alertText;
        if (error) {
            NSLog(@"%@",error);
            NSLog(@"%@", _postParams);
            alertText = [NSString stringWithFormat:
                      @"error: domain = %@, code = %d",
                      error.domain, error.code];
        } else {
            alertText = [NSString stringWithFormat:
                      @"Posted action, id: %@",
                      [result objectForKey:@"id"]];
        }
        // Show the result in an alert
        [[[UIAlertView alloc] initWithTitle:@"Result"
                                 message:alertText
                                delegate:self
                       cancelButtonTitle:@"OK!"
                       otherButtonTitles:nil]
        show];
    }];
}

I think, that the actual params are not being uploaded. I've been searching for several days trying to find a solution. Anyone have an idea of how to fix this and get the post to complete? Any help would be greatly appreciated!