just had a quick google and this came up hope it helps ;
• You aren't connected to the Internet. Connect to the Internet and then try again.
• There is a temporary problem with the store's server (it might be busy or it might not be online). Try again later.
• You had a subscription account with an online store, but you cancelled the subscription. Contact the online store about reinstating your subscription account or purchasing the file.
• The rights prohibit the action you are trying to perform. For example, the online store might grant you the right to burn a song to a CD five times, but you have exceeded the limit. Or the online store might not permit you to sync the file to a portable device. For more information, contact your online store.
• Your online store doesn't have your current billing information, such as your credit card number or expiration date. Go to the online store's Web site and try updating your billing information.
• Your online store requires you to log in, but you haven't entered a valid user name or password. Contact your online store for further assistance.
• Your online store requires that you install a more recent version of the Player or some security components and you have opted not to install the software. When prompted to install the software, do so.
• Your online store requires that you install a more recent version of the Player or some security components but the software is not yet available for your version of Windows. Either upgrade to the required version of Windows or wait until the software is available for your version
