Thanks a lot for the reply.
I saw the project and the file upload works like charm. The only thing i was missing in my project is the resource file, I have tried adding it and see if the Resource Not found issue was solved, but no luck. I have verified web config design code in Default.aspx and code behind also, I could not find any missing thing in my project.
To give more information, Our website is built and integrated in Sitefinity and the user control i tried RadAsyncUpload is inside a wizard control. Do I have to add anything else ?