Thank you for using answers.slingbox.com! I apologize for the inconvenience of not being able to connect to your Slingbox 350 via Mac computer. How are you connecting to the Slingbox? Are you going to newwatch.slingbox.com and choosing the Slingbox 350 from the Directory? This is how you would do so via computer.
Also, what operating system is the mac currently running on? It would need to be 10.6 or higher.
Below is a link to an article that explains what operating systems you need to use the Slingbox 350:
Hope this helps!
The Sling Moderation Team