app crashes on NSURLCONNECTION when multiple request

Question

Hey guyz I have this issue regarding the NSUrlConnection where I initiate a request like this

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:[NSString stringWithFormat:URL_PACKAGE,2]]];
Communication *comm = [[Communication alloc] initWithUrlRequest:request];
comm.request_name = request_name;
comm.delegate = self;
[comm startAsynchronous];
[request release];

and then the response getting code is fine but as you can see I have created a communication class to make the connection and when I request with difference web services it

- (Communication *) initWithUrlRequest:(NSMutableURLRequest *)url_request {
    self.request = url_request;
    return self;
}

-(void)dealloc {
    [super dealloc];
}

- (void) startAsynchronous {
    responseData = [[NSMutableData data] retain];
    NSLog(@"%@",[request URL]);
    downloadConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];  
}

-(void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response {
    [responseData setLength:0];
    if ( [[self delegate] respondsToSelector:@selector(communication:didReceiveResponse:RequestName:)] ) {
        [self.delegate communication:self didReceiveResponse:response RequestName:self.request_name];   
    } 
}

-(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data {
    [responseData appendData:data];
    if ( [[self delegate] respondsToSelector:@selector(communication:didReceiveData:RequestName:)] ) {
        [self.delegate communication:self didReceiveData:data RequestName:self.request_name];
    }
}

-(void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error {
    [self.delegate communication:self didFailWithError:error RequestName:self.request_name];
    NSLog(@"%@", error);
}

-(void)connectionDidFinishLoading:(NSURLConnection*)connection {
    NSString *responseString = [[[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding] autorelease];
    [responseData release];
    responseString = [responseString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    responseString = [responseString stringByReplacingOccurrencesOfString:@"+" withString:@" "];
    responseString = [responseString stringByReplacingOccurrencesOfString:@"null" withString:@"\"\""];

    [self.delegate communication:self didFinishWithString:responseString RequestName:self.request_name];
}

The error is

2013-07-30 13:55:46.994 Ipad Qld[3982:c07] *** -[Requests respondsToSelector:]: message sent to deallocated instance 0xa16b310