I tried both miners, letting MultiMiner download and install them and started the app first directly from Downloads, then from Programs. Try to start the miner in a Terminal next.
No need to move the app. I just wanted to know where it was so I could give direction.
Open Spotlight or Applications and launch Terminal.app and type the following:
/Applications/MultiMiner-1.1.19.app/Contents/Resources/Miners/bfgminer/bin/bfgminer -d?
The path is specific (that's if you dragged the app to Applications) and the version is specific as well, that's if you downloaded 1.1.19. Let me know the output of bfgminer. Mine looks like:
/Applications/MultiMiner-1.1.20.app/Contents/Resources/Miners/bfgminer/bin/bfgminer -d?
[2013-08-23 21:35:16] Started bfgminer 3.1.4
[2013-08-23 21:35:17] Devices detected:
[2013-08-23 21:35:17] 0. OCL 0 (driver: opencl)
[2013-08-23 21:35:17] 1. OCL 1 (driver: opencl)
2 devices listed