music download problem

> Hi,
> I have downloaded music tracks from tesco.com after sampling them.
> When I try to listen to them I find an exclamation mark beside the track
> name & I receive the message:
>
> A security upgrade is required to play this file. Do you want to download
> this upgrade? Upgrading may take a few minutes.
>
> When I attempt the download (at least 20 times so far on different days at
> different times) I receive the message:
>
> A problem occurred during security upgrade. try again later.
>
> Could someone help by explaining what is happening & if possible what I
> should do to enable me to listen to & transfer the tracks to my MP3 player.
> thanks
> Colin
>
>