no audio using "line-in" on dock

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I have a T410 and mini dock plus series 3.
I've connected my XM radio to the line-in on the dock, but I get no music.
This worked fine with my T61 & dock. Just wondering what as changed and if there's a work-around.
Been digging for a setting, but can find nothing.
Is the a Win7 or Thinkpad/dock issue?

Many thanks,
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