The problem mainly is that here at forums aren't that much people with experience on Mac OsX and thus it's difficult to give help when you're not on Windows or Linux. The second problem is that Apple handles Java different for their products - mainly because of their own support philosophy. Afaik the official Apple Java is still version 6 , while Oracle Java 7 and 8 aren't officially supported by Apple.
So my recommendation on MacOsX is to stay with what Apple supports (unless your not a Computerspecialist), which means to follow their guidelines also.
There's a reason why Macs are that expensive ...
Suggestion: check at Apple Support pages which is the recommended Java for your OsX Version i.e.
http://support.apple.com/kb/HT6133 (not sure if this is the right one or latest), check at other Mac related forums about uninstalling Oracle Java 7 or how to set Security Settings and such on how to run .jnlp files
It's not a Bug in HnH client but how Aple handles Java stuff ... alternativly you can try to run the Ender client by using the updater.jar with your installed Java 7 - but that means you have to search and read about running custom clients here at forums
Ender client thread
http://www.havenandhearth.com/forum/vie ... 75#p165075Ender run.bat and .command hints thread
viewtopic.php?f=27&t=35224older HnH on Mac thread
viewtopic.php?f=27&t=32796hth