I've discovered that on OSX 10.11, El Capitan, at least. that if you Edit Manually, to edit the bfguils.conf file, it introduces oddities that Jason falls over, and MacMiner refuses to start.
You MUST create and edit that file in vi, or vim as its often called. PURE text. I don't know what the MacMiner built in editor is doing, but it introduces hidden, bad characters in.
The file lives in /Users/your-name/Library/Application Support/MacMiner/bfguils.conf
to get to it, change to that directory from Terminal, and use vi to create the file.
Use this with the inverted commas.
Stop MacMiner - close it down.
cd "/Users/your-name/Library/Application Support/MacMiner"
Start MacMiner - hope for the best. This has been driving me NUTS for days now. But I think I discovered it. Don't edit it from within MacMiner - ever. The moment you do, it's stuffed and NOTHING you do to that file will clean it.
I've tried other text editors - no go. Nothing works for me except vi.