ipad app and sharepoint web service

Hello All,

I have an app in iPad and it retrieves data from Sharepoint server 2010.

There is a custom web service to retrieve the data from sharepoint to iPAd app.

Data is correctly retrieved and image urls are also retrieved with response.

iPad app is setting the Picture library image url so it will request the image from sharepoint server. 

in this case there will be 2 request and response 1.) 401 authentication challenge and 2.) 200 HTTPStatus  OK then only image is displayed in iPad app

In so many images after 401 authentication challenge no 200 HTTPStatus OK found not sure what exactly is happening in iPAd app requests.

Can some one please suggest on this.?

Thanks

Saumil