This issue should be resolved with patch 2.0.2 that is being deployed today. As other region patching times may vary, check your version of Diablo III on the Battle.net App window, next to the Play button.
If your version is below 126.96.36.19974, the patch may not have been deployed in your region. Check the Service Status forums for your region for upcoming maintenance times.
Greetings Mac Community!
We're aware of a crashing issue when opening the Auction House on OS X systems. Our teams are working to resolve this in a future update. In order to prevent Diablo III from crashing, it is recommended to avoid opening the Auction House (and any AH related UI) until the issue is resolved. We'll provide additional updates when more information is available.
We apologize about for any inconvenience this has caused, and hope to have this resolved as soon as possible.