Radio Buttons Affected By sScrollY

Bit confused by this, I have some radio buttons in my table which I set a default on (using 'checked'). Using zero configuration this works as expected, but if I add

"sScrollY": "300px",
"bPaginate": false

it doesn't!

Here's a simple test case: http://live.datatables.net/ocabay/3/edit#preview. The top of the two tables is zero configuration, the bottom adds the code above.

Any suggestions gratefully received.

Steph