Which slimport cable did you buy, specifically. This is the official slimport cable: http://www.amazon.com/SlimPort-HDMI-Adapter-Connect-enabled/dp/B00DWGB6CU/

It sounds like you got a cheap, generic version, that doesnt appear to be working well for you. I would send it back and get a refund.

Looks like the product has incredibly bad reviews, (33) 1star reviews. Sounds like its just a crappy product: http://www.amazon.com/Cable-Matters-SlimPort-Adapter-Charging/dp/B00EPMF504/

Sorry.