AFAIK, ATI's TV tuner software doesn't run in X. Not to mention that the software itself is a piece of crap. It is a bug ridden piece of crap, and they haven't done a major overhaul of it since they begin shipping it with the original Rage II XClaim VR.
I've had the (dis)pleasure of reviewing pretty much every ATI card they've shipped over the past five years or so, and the only one that ever really got to me was the VR series, simply because the software was awful.
At a press meeting over a year ago, ATI said they were trying to move away from the VR series of cards and try and offer TV Tuner functionality in external devices like the USB tuner. They continue to decline to comment as to whether or not there will ever be an OS X version.
There are some other solutions out there... been up all night and can't think of the names