Finally I got this
Last login: Sat Nov 30 14:47:25 on ttys000
CAT-cpence:~ cpence$ mono ~/Downloads/MultiMiner.app/Contents/Resources/MultiMiner.Win.exe
System.IO.DirectoryNotFoundException: Directory '/Users/cpence/Downloads/MultiMiner.app/Contents/Resources/Miners/bfgminer' not found.
at System.IO.Directory.ValidateDirectoryListing (System.String path, System.String searchPattern, System.Boolean& stop) [0x00000] in :0
at System.IO.Directory.GetFileSystemEntries (System.String path, System.String searchPattern, FileAttributes mask, FileAttributes attrs) [0x00000] in :0
at System.IO.Directory.GetFiles (System.String path, System.String searchPattern) [0x00000] in :0
at System.IO.DirectoryInfo.GetFiles (System.String searchPattern) [0x00000] in :0
at System.IO.DirectoryInfo.GetFiles () [0x00000] in :0
at (wrapper remoting-invoke-with-check) System.IO.DirectoryInfo:GetFiles ()
at MultiMiner.Xgminer.Installer.DeleteFolderContents (System.String folderPath) [0x00000] in :0
at MultiMiner.Xgminer.Installer.InstallMiner (System.String destinationFolder) [0x00000] in :0
at MultiMiner.Win.MainForm.InstallMiner () [0x00000] in :0
Looks like an issue installing bfgminer. Can you please try installing it yourself before running MultiMiner? There are instructions for that here: