There is an issue with SlingPlayer on the Captivate so I woudln't recommend buying it until its fixed anyway. I asked about the issue here https://community.sling.com/message/13962#13962 but have yet to receive a resonse...
In this case, we recommend you to use the Android MarketPlace contact information, since we do not handle these situations. Just make sure to check this link.
Android Market Help
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