NASN (UK) How can they just stop broadcasting an event ?

Amazing.

I'm watching NASCAR, 11am, and what happens.
Screen goes blue, and that's it, race over for me with over 60 or so laps to go.

I called Sentanta who told me, the follwoing
1. They are having problems with some channels.
2. Operator cannot work out why I cannot view channel 434.
3. Oh sorry, Sentanta 434 is finished now, unlucky, thats that.

Told nothing can be done, maybe shown later.

Sentanta are beyond belief, this is just not right ?