There's another user having Mac crashes. Trying to troubleshoot again.
Evamaria, please try the attached version and see if it works any better.
See the How do I install a plugin manually? section of this thread
This is based on what I'd worked out with the previous user before other updates to their Mac system mysteriously fixed it.
If that doesn't work, please run calibre in debug mode (calibre-debug -g) in a command line/prompt window, try the plugin again and post the output from the command line/prompt window here along with the error text from the crash.