Thank you for using our online answers forum. I am sorry to hear your having issues getting video on your imac, that is definitely a little odd to say the least. It's hard to say what the exact culprit could be without a little more information. What operating system are you running on your imac? You don't have any issues on any other computer or your iphone correct? Here is a link on our supported browsers and operating systems to make sure you are meeting the minimum requirements, What browsers and systems are supported by Watch on Slingbox.com? Please let me know if this helps!
The Sling Moderation Team